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Calling a function from external file with dynamic module name [duplicate]

I'm writing a Python application that takes a command as an argument, for example:
$ python myapp.py command1
I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:
myapp/
__init__.py
commands/
__init__.py
command1.py
command2.py
foo.py
bar.py
So I want the application to find the available command modules at runtime and execute the appropriate one.
Python defines an __import__() function, which takes a string for a module name:
__import__(name, globals=None, locals=None, fromlist=(), level=0)
The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.
Source: https://docs.python.org/3/library/functions.html#__import__
So currently I have something like:
command = sys.argv[1]
try:
command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"])
except ImportError:
# Display error message
command_module.run()
This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.
Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.
See also: How do I import a module given the full path?

With Python older than 2.7/3.1, that's pretty much how you do it.
For newer versions, see importlib.import_module for Python 2 and Python 3.
Or using __import__ you can import a list of modules by doing this:
>>> moduleNames = ['sys', 'os', 're', 'unittest']
>>> moduleNames
['sys', 'os', 're', 'unittest']
>>> modules = map(__import__, moduleNames)
Ripped straight from Dive Into Python.

The recommended way for Python 2.7 and 3.1 and later is to use importlib module:
importlib.import_module(name, package=None)
Import a module. The name argument specifies what module to import in absolute or relative terms (e.g. either pkg.mod or ..mod). If the name is specified in relative terms, then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. import_module('..mod', 'pkg.subpkg') will import pkg.mod).
e.g.
my_module = importlib.import_module('os.path')

Note: imp is deprecated since Python 3.4 in favor of importlib
As mentioned the imp module provides you loading functions:
imp.load_source(name, path)
imp.load_compiled(name, path)
I've used these before to perform something similar.
In my case I defined a specific class with defined methods that were required.
Once I loaded the module I would check if the class was in the module, and then create an instance of that class, something like this:
import imp
import os
def load_from_file(filepath):
class_inst = None
expected_class = 'MyClass'
mod_name,file_ext = os.path.splitext(os.path.split(filepath)[-1])
if file_ext.lower() == '.py':
py_mod = imp.load_source(mod_name, filepath)
elif file_ext.lower() == '.pyc':
py_mod = imp.load_compiled(mod_name, filepath)
if hasattr(py_mod, expected_class):
class_inst = getattr(py_mod, expected_class)()
return class_inst

Using importlib
Importing a source file
Here is a slightly adapted example from the documentation:
import sys
import importlib.util
file_path = 'pluginX.py'
module_name = 'pluginX'
spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Verify contents of the module:
print(dir(module))
From here, module will be a module object representing the pluginX module (the same thing that would be assigned to pluginX by doing import pluginX). Thus, to call e.g. a hello function (with no parameters) defined in pluginX, use module.hello().
To get the effect "importing" functionality from the module instead, store it in the in-memory cache of loaded modules, and then do the corresponding from import:
sys.modules[module_name] = module
from pluginX import hello
hello()
Importing a package
To import a package instead, calling import_module is sufficient. Suppose there is a package folder pluginX in the current working directory; then just do
import importlib
pkg = importlib.import_module('pluginX')
# check if it's all there..
print(dir(pkg))

Use the imp module, or the more direct __import__() function.

You can use exec:
exec("import myapp.commands.%s" % command)

If you want it in your locals:
>>> mod = 'sys'
>>> locals()['my_module'] = __import__(mod)
>>> my_module.version
'2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)]'
same would work with globals()

Similar as #monkut 's solution but reusable and error tolerant described here http://stamat.wordpress.com/dynamic-module-import-in-python/:
import os
import imp
def importFromURI(uri, absl):
mod = None
if not absl:
uri = os.path.normpath(os.path.join(os.path.dirname(__file__), uri))
path, fname = os.path.split(uri)
mname, ext = os.path.splitext(fname)
if os.path.exists(os.path.join(path,mname)+'.pyc'):
try:
return imp.load_compiled(mname, uri)
except:
pass
if os.path.exists(os.path.join(path,mname)+'.py'):
try:
return imp.load_source(mname, uri)
except:
pass
return mod

The below piece worked for me:
>>>import imp;
>>>fp, pathname, description = imp.find_module("/home/test_module");
>>>test_module = imp.load_module("test_module", fp, pathname, description);
>>>print test_module.print_hello();
if you want to import in shell-script:
python -c '<above entire code in one line>'

The following worked for me:
import sys, glob
sys.path.append('/home/marc/python/importtest/modus')
fl = glob.glob('modus/*.py')
modulist = []
adapters=[]
for i in range(len(fl)):
fl[i] = fl[i].split('/')[1]
fl[i] = fl[i][0:(len(fl[i])-3)]
modulist.append(getattr(__import__(fl[i]),fl[i]))
adapters.append(modulist[i]())
It loads modules from the folder 'modus'. The modules have a single class with the same name as the module name. E.g. the file modus/modu1.py contains:
class modu1():
def __init__(self):
self.x=1
print self.x
The result is a list of dynamically loaded classes "adapters".

Possible to import a python file without knowing it's name? [duplicate]

I'm writing a Python application that takes a command as an argument, for example:
$ python myapp.py command1
I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:
myapp/
__init__.py
commands/
__init__.py
command1.py
command2.py
foo.py
bar.py
So I want the application to find the available command modules at runtime and execute the appropriate one.
Python defines an __import__() function, which takes a string for a module name:
__import__(name, globals=None, locals=None, fromlist=(), level=0)
The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.
Source: https://docs.python.org/3/library/functions.html#__import__
So currently I have something like:
command = sys.argv[1]
try:
command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"])
except ImportError:
# Display error message
command_module.run()
This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.
Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.
See also: How do I import a module given the full path?

With Python older than 2.7/3.1, that's pretty much how you do it.
For newer versions, see importlib.import_module for Python 2 and Python 3.
Or using __import__ you can import a list of modules by doing this:
>>> moduleNames = ['sys', 'os', 're', 'unittest']
>>> moduleNames
['sys', 'os', 're', 'unittest']
>>> modules = map(__import__, moduleNames)
Ripped straight from Dive Into Python.

The recommended way for Python 2.7 and 3.1 and later is to use importlib module:
importlib.import_module(name, package=None)
Import a module. The name argument specifies what module to import in absolute or relative terms (e.g. either pkg.mod or ..mod). If the name is specified in relative terms, then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. import_module('..mod', 'pkg.subpkg') will import pkg.mod).
e.g.
my_module = importlib.import_module('os.path')

Note: imp is deprecated since Python 3.4 in favor of importlib
As mentioned the imp module provides you loading functions:
imp.load_source(name, path)
imp.load_compiled(name, path)
I've used these before to perform something similar.
In my case I defined a specific class with defined methods that were required.
Once I loaded the module I would check if the class was in the module, and then create an instance of that class, something like this:
import imp
import os
def load_from_file(filepath):
class_inst = None
expected_class = 'MyClass'
mod_name,file_ext = os.path.splitext(os.path.split(filepath)[-1])
if file_ext.lower() == '.py':
py_mod = imp.load_source(mod_name, filepath)
elif file_ext.lower() == '.pyc':
py_mod = imp.load_compiled(mod_name, filepath)
if hasattr(py_mod, expected_class):
class_inst = getattr(py_mod, expected_class)()
return class_inst

Using importlib
Importing a source file
Here is a slightly adapted example from the documentation:
import sys
import importlib.util
file_path = 'pluginX.py'
module_name = 'pluginX'
spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Verify contents of the module:
print(dir(module))
From here, module will be a module object representing the pluginX module (the same thing that would be assigned to pluginX by doing import pluginX). Thus, to call e.g. a hello function (with no parameters) defined in pluginX, use module.hello().
To get the effect "importing" functionality from the module instead, store it in the in-memory cache of loaded modules, and then do the corresponding from import:
sys.modules[module_name] = module
from pluginX import hello
hello()
Importing a package
To import a package instead, calling import_module is sufficient. Suppose there is a package folder pluginX in the current working directory; then just do
import importlib
pkg = importlib.import_module('pluginX')
# check if it's all there..
print(dir(pkg))

Use the imp module, or the more direct __import__() function.

You can use exec:
exec("import myapp.commands.%s" % command)

If you want it in your locals:
>>> mod = 'sys'
>>> locals()['my_module'] = __import__(mod)
>>> my_module.version
'2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)]'
same would work with globals()

Similar as #monkut 's solution but reusable and error tolerant described here http://stamat.wordpress.com/dynamic-module-import-in-python/:
import os
import imp
def importFromURI(uri, absl):
mod = None
if not absl:
uri = os.path.normpath(os.path.join(os.path.dirname(__file__), uri))
path, fname = os.path.split(uri)
mname, ext = os.path.splitext(fname)
if os.path.exists(os.path.join(path,mname)+'.pyc'):
try:
return imp.load_compiled(mname, uri)
except:
pass
if os.path.exists(os.path.join(path,mname)+'.py'):
try:
return imp.load_source(mname, uri)
except:
pass
return mod

The below piece worked for me:
>>>import imp;
>>>fp, pathname, description = imp.find_module("/home/test_module");
>>>test_module = imp.load_module("test_module", fp, pathname, description);
>>>print test_module.print_hello();
if you want to import in shell-script:
python -c '<above entire code in one line>'

The following worked for me:
import sys, glob
sys.path.append('/home/marc/python/importtest/modus')
fl = glob.glob('modus/*.py')
modulist = []
adapters=[]
for i in range(len(fl)):
fl[i] = fl[i].split('/')[1]
fl[i] = fl[i][0:(len(fl[i])-3)]
modulist.append(getattr(__import__(fl[i]),fl[i]))
adapters.append(modulist[i]())
It loads modules from the folder 'modus'. The modules have a single class with the same name as the module name. E.g. the file modus/modu1.py contains:
class modu1():
def __init__(self):
self.x=1
print self.x
The result is a list of dynamically loaded classes "adapters".

Can we import a module by tracing it which is not in sys.path, instead it is in some child folder of my CWD [duplicate]

How do I load a Python module given its full path?
Note that the file can be anywhere in the filesystem where the user has access rights.
See also: How to import a module given its name as string?

For Python 3.5+ use (docs):
import importlib.util
import sys
spec = importlib.util.spec_from_file_location("module.name", "/path/to/file.py")
foo = importlib.util.module_from_spec(spec)
sys.modules["module.name"] = foo
spec.loader.exec_module(foo)
foo.MyClass()
For Python 3.3 and 3.4 use:
from importlib.machinery import SourceFileLoader
foo = SourceFileLoader("module.name", "/path/to/file.py").load_module()
foo.MyClass()
(Although this has been deprecated in Python 3.4.)
For Python 2 use:
import imp
foo = imp.load_source('module.name', '/path/to/file.py')
foo.MyClass()
There are equivalent convenience functions for compiled Python files and DLLs.
See also http://bugs.python.org/issue21436.

The advantage of adding a path to sys.path (over using imp) is that it simplifies things when importing more than one module from a single package. For example:
import sys
# the mock-0.3.1 dir contains testcase.py, testutils.py & mock.py
sys.path.append('/foo/bar/mock-0.3.1')
from testcase import TestCase
from testutils import RunTests
from mock import Mock, sentinel, patch

To import your module, you need to add its directory to the environment variable, either temporarily or permanently.
Temporarily
import sys
sys.path.append("/path/to/my/modules/")
import my_module
Permanently
Adding the following line to your .bashrc (or alternative) file in Linux
and excecute source ~/.bashrc (or alternative) in the terminal:
export PYTHONPATH="${PYTHONPATH}:/path/to/my/modules/"
Credit/Source: saarrrr, another Stack Exchange question

If your top-level module is not a file but is packaged as a directory with __init__.py, then the accepted solution almost works, but not quite. In Python 3.5+ the following code is needed (note the added line that begins with 'sys.modules'):
MODULE_PATH = "/path/to/your/module/__init__.py"
MODULE_NAME = "mymodule"
import importlib
import sys
spec = importlib.util.spec_from_file_location(MODULE_NAME, MODULE_PATH)
module = importlib.util.module_from_spec(spec)
sys.modules[spec.name] = module
spec.loader.exec_module(module)
Without this line, when exec_module is executed, it tries to bind relative imports in your top level __init__.py to the top level module name -- in this case "mymodule". But "mymodule" isn't loaded yet so you'll get the error "SystemError: Parent module 'mymodule' not loaded, cannot perform relative import". So you need to bind the name before you load it. The reason for this is the fundamental invariant of the relative import system: "The invariant holding is that if you have sys.modules['spam'] and sys.modules['spam.foo'] (as you would after the above import), the latter must appear as the foo attribute of the former" as discussed here.

It sounds like you don't want to specifically import the configuration file (which has a whole lot of side effects and additional complications involved). You just want to run it, and be able to access the resulting namespace. The standard library provides an API specifically for that in the form of runpy.run_path:
from runpy import run_path
settings = run_path("/path/to/file.py")
That interface is available in Python 2.7 and Python 3.2+.

You can also do something like this and add the directory that the configuration file is sitting in to the Python load path, and then just do a normal import, assuming you know the name of the file in advance, in this case "config".
Messy, but it works.
configfile = '~/config.py'
import os
import sys
sys.path.append(os.path.dirname(os.path.expanduser(configfile)))
import config

I have come up with a slightly modified version of #SebastianRittau's wonderful answer (for Python > 3.4 I think), which will allow you to load a file with any extension as a module using spec_from_loader instead of spec_from_file_location:
from importlib.util import spec_from_loader, module_from_spec
from importlib.machinery import SourceFileLoader
spec = spec_from_loader("module.name", SourceFileLoader("module.name", "/path/to/file.py"))
mod = module_from_spec(spec)
spec.loader.exec_module(mod)
The advantage of encoding the path in an explicit SourceFileLoader is that the machinery will not try to figure out the type of the file from the extension. This means that you can load something like a .txt file using this method, but you could not do it with spec_from_file_location without specifying the loader because .txt is not in importlib.machinery.SOURCE_SUFFIXES.
I've placed an implementation based on this, and #SamGrondahl's useful modification into my utility library, haggis. The function is called haggis.load.load_module. It adds a couple of neat tricks, like the ability to inject variables into the module namespace as it is loaded.

You can use the
load_source(module_name, path_to_file)
method from the imp module.

Do you mean load or import?
You can manipulate the sys.path list specify the path to your module, and then import your module. For example, given a module at:
/foo/bar.py
You could do:
import sys
sys.path[0:0] = ['/foo'] # Puts the /foo directory at the start of your path
import bar

Here is some code that works in all Python versions, from 2.7-3.5 and probably even others.
config_file = "/tmp/config.py"
with open(config_file) as f:
code = compile(f.read(), config_file, 'exec')
exec(code, globals(), locals())
I tested it. It may be ugly, but so far it is the only one that works in all versions.

You can do this using __import__ and chdir:
def import_file(full_path_to_module):
try:
import os
module_dir, module_file = os.path.split(full_path_to_module)
module_name, module_ext = os.path.splitext(module_file)
save_cwd = os.getcwd()
os.chdir(module_dir)
module_obj = __import__(module_name)
module_obj.__file__ = full_path_to_module
globals()[module_name] = module_obj
os.chdir(save_cwd)
except Exception as e:
raise ImportError(e)
return module_obj
import_file('/home/somebody/somemodule.py')

If we have scripts in the same project but in different directory means, we can solve this problem by the following method.
In this situation utils.py is in src/main/util/
import sys
sys.path.append('./')
import src.main.util.utils
#or
from src.main.util.utils import json_converter # json_converter is example method

To add to Sebastian Rittau's answer:
At least for CPython, there's pydoc, and, while not officially declared, importing files is what it does:
from pydoc import importfile
module = importfile('/path/to/module.py')
PS. For the sake of completeness, there's a reference to the current implementation at the moment of writing: pydoc.py, and I'm pleased to say that in the vein of xkcd 1987 it uses neither of the implementations mentioned in issue 21436 -- at least, not verbatim.

I believe you can use imp.find_module() and imp.load_module() to load the specified module. You'll need to split the module name off of the path, i.e. if you wanted to load /home/mypath/mymodule.py you'd need to do:
imp.find_module('mymodule', '/home/mypath/')
...but that should get the job done.

You can use the pkgutil module (specifically the walk_packages method) to get a list of the packages in the current directory. From there it's trivial to use the importlib machinery to import the modules you want:
import pkgutil
import importlib
packages = pkgutil.walk_packages(path='.')
for importer, name, is_package in packages:
mod = importlib.import_module(name)
# do whatever you want with module now, it's been imported!

There's a package that's dedicated to this specifically:
from thesmuggler import smuggle
# À la `import weapons`
weapons = smuggle('weapons.py')
# À la `from contraband import drugs, alcohol`
drugs, alcohol = smuggle('drugs', 'alcohol', source='contraband.py')
# À la `from contraband import drugs as dope, alcohol as booze`
dope, booze = smuggle('drugs', 'alcohol', source='contraband.py')
It's tested across Python versions (Jython and PyPy too), but it might be overkill depending on the size of your project.

Create Python module test.py:
import sys
sys.path.append("<project-path>/lib/")
from tes1 import Client1
from tes2 import Client2
import tes3
Create Python module test_check.py:
from test import Client1
from test import Client2
from test import test3
We can import the imported module from module.

This area of Python 3.4 seems to be extremely tortuous to understand! However with a bit of hacking using the code from Chris Calloway as a start I managed to get something working. Here's the basic function.
def import_module_from_file(full_path_to_module):
"""
Import a module given the full path/filename of the .py file
Python 3.4
"""
module = None
try:
# Get module name and path from full path
module_dir, module_file = os.path.split(full_path_to_module)
module_name, module_ext = os.path.splitext(module_file)
# Get module "spec" from filename
spec = importlib.util.spec_from_file_location(module_name,full_path_to_module)
module = spec.loader.load_module()
except Exception as ec:
# Simple error printing
# Insert "sophisticated" stuff here
print(ec)
finally:
return module
This appears to use non-deprecated modules from Python 3.4. I don't pretend to understand why, but it seems to work from within a program. I found Chris' solution worked on the command line but not from inside a program.

I made a package that uses imp for you. I call it import_file and this is how it's used:
>>>from import_file import import_file
>>>mylib = import_file('c:\\mylib.py')
>>>another = import_file('relative_subdir/another.py')
You can get it at:
http://pypi.python.org/pypi/import_file
or at
http://code.google.com/p/import-file/

To import a module from a given filename, you can temporarily extend the path, and restore the system path in the finally block reference:
filename = "directory/module.py"
directory, module_name = os.path.split(filename)
module_name = os.path.splitext(module_name)[0]
path = list(sys.path)
sys.path.insert(0, directory)
try:
module = __import__(module_name)
finally:
sys.path[:] = path # restore

A simple solution using importlib instead of the imp package (tested for Python 2.7, although it should work for Python 3 too):
import importlib
dirname, basename = os.path.split(pyfilepath) # pyfilepath: '/my/path/mymodule.py'
sys.path.append(dirname) # only directories should be added to PYTHONPATH
module_name = os.path.splitext(basename)[0] # '/my/path/mymodule.py' --> 'mymodule'
module = importlib.import_module(module_name) # name space of defined module (otherwise we would literally look for "module_name")
Now you can directly use the namespace of the imported module, like this:
a = module.myvar
b = module.myfunc(a)
The advantage of this solution is that we don't even need to know the actual name of the module we would like to import, in order to use it in our code. This is useful, e.g. in case the path of the module is a configurable argument.

I have written my own global and portable import function, based on importlib module, for:
Be able to import both modules as submodules and to import the content of a module to a parent module (or into a globals if has no parent module).
Be able to import modules with a period characters in a file name.
Be able to import modules with any extension.
Be able to use a standalone name for a submodule instead of a file name without extension which is by default.
Be able to define the import order based on previously imported module instead of dependent on sys.path or on a what ever search path storage.
The examples directory structure:
<root>
|
+- test.py
|
+- testlib.py
|
+- /std1
| |
| +- testlib.std1.py
|
+- /std2
| |
| +- testlib.std2.py
|
+- /std3
|
+- testlib.std3.py
Inclusion dependency and order:
test.py
-> testlib.py
-> testlib.std1.py
-> testlib.std2.py
-> testlib.std3.py
Implementation:
Latest changes store: https://sourceforge.net/p/tacklelib/tacklelib/HEAD/tree/trunk/python/tacklelib/tacklelib.py
test.py:
import os, sys, inspect, copy
SOURCE_FILE = os.path.abspath(inspect.getsourcefile(lambda:0)).replace('\\','/')
SOURCE_DIR = os.path.dirname(SOURCE_FILE)
print("test::SOURCE_FILE: ", SOURCE_FILE)
# portable import to the global space
sys.path.append(TACKLELIB_ROOT) # TACKLELIB_ROOT - path to the library directory
import tacklelib as tkl
tkl.tkl_init(tkl)
# cleanup
del tkl # must be instead of `tkl = None`, otherwise the variable would be still persist
sys.path.pop()
tkl_import_module(SOURCE_DIR, 'testlib.py')
print(globals().keys())
testlib.base_test()
testlib.testlib_std1.std1_test()
testlib.testlib_std1.testlib_std2.std2_test()
#testlib.testlib.std3.std3_test() # does not reachable directly ...
getattr(globals()['testlib'], 'testlib.std3').std3_test() # ... but reachable through the `globals` + `getattr`
tkl_import_module(SOURCE_DIR, 'testlib.py', '.')
print(globals().keys())
base_test()
testlib_std1.std1_test()
testlib_std1.testlib_std2.std2_test()
#testlib.std3.std3_test() # does not reachable directly ...
globals()['testlib.std3'].std3_test() # ... but reachable through the `globals` + `getattr`
testlib.py:
# optional for 3.4.x and higher
#import os, inspect
#
#SOURCE_FILE = os.path.abspath(inspect.getsourcefile(lambda:0)).replace('\\','/')
#SOURCE_DIR = os.path.dirname(SOURCE_FILE)
print("1 testlib::SOURCE_FILE: ", SOURCE_FILE)
tkl_import_module(SOURCE_DIR + '/std1', 'testlib.std1.py', 'testlib_std1')
# SOURCE_DIR is restored here
print("2 testlib::SOURCE_FILE: ", SOURCE_FILE)
tkl_import_module(SOURCE_DIR + '/std3', 'testlib.std3.py')
print("3 testlib::SOURCE_FILE: ", SOURCE_FILE)
def base_test():
print('base_test')
testlib.std1.py:
# optional for 3.4.x and higher
#import os, inspect
#
#SOURCE_FILE = os.path.abspath(inspect.getsourcefile(lambda:0)).replace('\\','/')
#SOURCE_DIR = os.path.dirname(SOURCE_FILE)
print("testlib.std1::SOURCE_FILE: ", SOURCE_FILE)
tkl_import_module(SOURCE_DIR + '/../std2', 'testlib.std2.py', 'testlib_std2')
def std1_test():
print('std1_test')
testlib.std2.py:
# optional for 3.4.x and higher
#import os, inspect
#
#SOURCE_FILE = os.path.abspath(inspect.getsourcefile(lambda:0)).replace('\\','/')
#SOURCE_DIR = os.path.dirname(SOURCE_FILE)
print("testlib.std2::SOURCE_FILE: ", SOURCE_FILE)
def std2_test():
print('std2_test')
testlib.std3.py:
# optional for 3.4.x and higher
#import os, inspect
#
#SOURCE_FILE = os.path.abspath(inspect.getsourcefile(lambda:0)).replace('\\','/')
#SOURCE_DIR = os.path.dirname(SOURCE_FILE)
print("testlib.std3::SOURCE_FILE: ", SOURCE_FILE)
def std3_test():
print('std3_test')
Output (3.7.4):
test::SOURCE_FILE: <root>/test01/test.py
import : <root>/test01/testlib.py as testlib -> []
1 testlib::SOURCE_FILE: <root>/test01/testlib.py
import : <root>/test01/std1/testlib.std1.py as testlib_std1 -> ['testlib']
import : <root>/test01/std1/../std2/testlib.std2.py as testlib_std2 -> ['testlib', 'testlib_std1']
testlib.std2::SOURCE_FILE: <root>/test01/std1/../std2/testlib.std2.py
2 testlib::SOURCE_FILE: <root>/test01/testlib.py
import : <root>/test01/std3/testlib.std3.py as testlib.std3 -> ['testlib']
testlib.std3::SOURCE_FILE: <root>/test01/std3/testlib.std3.py
3 testlib::SOURCE_FILE: <root>/test01/testlib.py
dict_keys(['__name__', '__doc__', '__package__', '__loader__', '__spec__', '__annotations__', '__builtins__', '__file__', '__cached__', 'os', 'sys', 'inspect', 'copy', 'SOURCE_FILE', 'SOURCE_DIR', 'TackleGlobalImportModuleState', 'tkl_membercopy', 'tkl_merge_module', 'tkl_get_parent_imported_module_state', 'tkl_declare_global', 'tkl_import_module', 'TackleSourceModuleState', 'tkl_source_module', 'TackleLocalImportModuleState', 'testlib'])
base_test
std1_test
std2_test
std3_test
import : <root>/test01/testlib.py as . -> []
1 testlib::SOURCE_FILE: <root>/test01/testlib.py
import : <root>/test01/std1/testlib.std1.py as testlib_std1 -> ['testlib']
import : <root>/test01/std1/../std2/testlib.std2.py as testlib_std2 -> ['testlib', 'testlib_std1']
testlib.std2::SOURCE_FILE: <root>/test01/std1/../std2/testlib.std2.py
2 testlib::SOURCE_FILE: <root>/test01/testlib.py
import : <root>/test01/std3/testlib.std3.py as testlib.std3 -> ['testlib']
testlib.std3::SOURCE_FILE: <root>/test01/std3/testlib.std3.py
3 testlib::SOURCE_FILE: <root>/test01/testlib.py
dict_keys(['__name__', '__doc__', '__package__', '__loader__', '__spec__', '__annotations__', '__builtins__', '__file__', '__cached__', 'os', 'sys', 'inspect', 'copy', 'SOURCE_FILE', 'SOURCE_DIR', 'TackleGlobalImportModuleState', 'tkl_membercopy', 'tkl_merge_module', 'tkl_get_parent_imported_module_state', 'tkl_declare_global', 'tkl_import_module', 'TackleSourceModuleState', 'tkl_source_module', 'TackleLocalImportModuleState', 'testlib', 'testlib_std1', 'testlib.std3', 'base_test'])
base_test
std1_test
std2_test
std3_test
Tested in Python 3.7.4, 3.2.5, 2.7.16
Pros:
Can import both module as a submodule and can import content of a module to a parent module (or into a globals if has no parent module).
Can import modules with periods in a file name.
Can import any extension module from any extension module.
Can use a standalone name for a submodule instead of a file name without extension which is by default (for example, testlib.std.py as testlib, testlib.blabla.py as testlib_blabla and so on).
Does not depend on a sys.path or on a what ever search path storage.
Does not require to save/restore global variables like SOURCE_FILE and SOURCE_DIR between calls to tkl_import_module.
[for 3.4.x and higher] Can mix the module namespaces in nested tkl_import_module calls (ex: named->local->named or local->named->local and so on).
[for 3.4.x and higher] Can auto export global variables/functions/classes from where being declared to all children modules imported through the tkl_import_module (through the tkl_declare_global function).
Cons:
Does not support complete import:
Ignores enumerations and subclasses.
Ignores builtins because each what type has to be copied exclusively.
Ignore not trivially copiable classes.
Avoids copying builtin modules including all packaged modules.
[for 3.3.x and lower] Require to declare tkl_import_module in all modules which calls to tkl_import_module (code duplication)
Update 1,2 (for 3.4.x and higher only):
In Python 3.4 and higher you can bypass the requirement to declare tkl_import_module in each module by declare tkl_import_module in a top level module and the function would inject itself to all children modules in a single call (it's a kind of self deploy import).
Update 3:
Added function tkl_source_module as analog to bash source with support execution guard upon import (implemented through the module merge instead of import).
Update 4:
Added function tkl_declare_global to auto export a module global variable to all children modules where a module global variable is not visible because is not a part of a child module.
Update 5:
All functions has moved into the tacklelib library, see the link above.

This should work
path = os.path.join('./path/to/folder/with/py/files', '*.py')
for infile in glob.glob(path):
basename = os.path.basename(infile)
basename_without_extension = basename[:-3]
# http://docs.python.org/library/imp.html?highlight=imp#module-imp
imp.load_source(basename_without_extension, infile)

Import package modules at runtime (Python recipe)
http://code.activestate.com/recipes/223972/
###################
## #
## classloader.py #
## #
###################
import sys, types
def _get_mod(modulePath):
try:
aMod = sys.modules[modulePath]
if not isinstance(aMod, types.ModuleType):
raise KeyError
except KeyError:
# The last [''] is very important!
aMod = __import__(modulePath, globals(), locals(), [''])
sys.modules[modulePath] = aMod
return aMod
def _get_func(fullFuncName):
"""Retrieve a function object from a full dotted-package name."""
# Parse out the path, module, and function
lastDot = fullFuncName.rfind(u".")
funcName = fullFuncName[lastDot + 1:]
modPath = fullFuncName[:lastDot]
aMod = _get_mod(modPath)
aFunc = getattr(aMod, funcName)
# Assert that the function is a *callable* attribute.
assert callable(aFunc), u"%s is not callable." % fullFuncName
# Return a reference to the function itself,
# not the results of the function.
return aFunc
def _get_class(fullClassName, parentClass=None):
"""Load a module and retrieve a class (NOT an instance).
If the parentClass is supplied, className must be of parentClass
or a subclass of parentClass (or None is returned).
"""
aClass = _get_func(fullClassName)
# Assert that the class is a subclass of parentClass.
if parentClass is not None:
if not issubclass(aClass, parentClass):
raise TypeError(u"%s is not a subclass of %s" %
(fullClassName, parentClass))
# Return a reference to the class itself, not an instantiated object.
return aClass
######################
## Usage ##
######################
class StorageManager: pass
class StorageManagerMySQL(StorageManager): pass
def storage_object(aFullClassName, allOptions={}):
aStoreClass = _get_class(aFullClassName, StorageManager)
return aStoreClass(allOptions)

I'm not saying that it is better, but for the sake of completeness, I wanted to suggest the exec function, available in both Python 2 and Python 3.
exec allows you to execute arbitrary code in either the global scope, or in an internal scope, provided as a dictionary.
For example, if you have a module stored in "/path/to/module" with the function foo(), you could run it by doing the following:
module = dict()
with open("/path/to/module") as f:
exec(f.read(), module)
module['foo']()
This makes it a bit more explicit that you're loading code dynamically, and grants you some additional power, such as the ability to provide custom builtins.
And if having access through attributes, instead of keys is important to you, you can design a custom dict class for the globals, that provides such access, e.g.:
class MyModuleClass(dict):
def __getattr__(self, name):
return self.__getitem__(name)

In Linux, adding a symbolic link in the directory your Python script is located works.
I.e.:
ln -s /absolute/path/to/module/module.py /absolute/path/to/script/module.py
The Python interpreter will create /absolute/path/to/script/module.pyc and will update it if you change the contents of /absolute/path/to/module/module.py.
Then include the following in file mypythonscript.py:
from module import *

This will allow imports of compiled (pyd) Python modules in 3.4:
import sys
import importlib.machinery
def load_module(name, filename):
# If the Loader finds the module name in this list it will use
# module_name.__file__ instead so we need to delete it here
if name in sys.modules:
del sys.modules[name]
loader = importlib.machinery.ExtensionFileLoader(name, filename)
module = loader.load_module()
locals()[name] = module
globals()[name] = module
load_module('something', r'C:\Path\To\something.pyd')
something.do_something()

A quite simple way: suppose you want import file with relative path ../../MyLibs/pyfunc.py
libPath = '../../MyLibs'
import sys
if not libPath in sys.path: sys.path.append(libPath)
import pyfunc as pf
But if you make it without a guard you can finally get a very long path.

These are my two utility functions using only pathlib. It infers the module name from the path.
By default, it recursively loads all Python files from folders and replaces init.py by the parent folder name. But you can also give a Path and/or a glob to select some specific files.
from pathlib import Path
from importlib.util import spec_from_file_location, module_from_spec
from typing import Optional
def get_module_from_path(path: Path, relative_to: Optional[Path] = None):
if not relative_to:
relative_to = Path.cwd()
abs_path = path.absolute()
relative_path = abs_path.relative_to(relative_to.absolute())
if relative_path.name == "__init__.py":
relative_path = relative_path.parent
module_name = ".".join(relative_path.with_suffix("").parts)
mod = module_from_spec(spec_from_file_location(module_name, path))
return mod
def get_modules_from_folder(folder: Optional[Path] = None, glob_str: str = "*/**/*.py"):
if not folder:
folder = Path(".")
mod_list = []
for file_path in sorted(folder.glob(glob_str)):
mod_list.append(get_module_from_path(file_path))
return mod_list

This answer is a supplement to Sebastian Rittau's answer responding to the comment: "but what if you don't have the module name?" This is a quick and dirty way of getting the likely Python module name given a filename -- it just goes up the tree until it finds a directory without an __init__.py file and then turns it back into a filename. For Python 3.4+ (uses pathlib), which makes sense since Python 2 people can use "imp" or other ways of doing relative imports:
import pathlib
def likely_python_module(filename):
'''
Given a filename or Path, return the "likely" python module name. That is, iterate
the parent directories until it doesn't contain an __init__.py file.
:rtype: str
'''
p = pathlib.Path(filename).resolve()
paths = []
if p.name != '__init__.py':
paths.append(p.stem)
while True:
p = p.parent
if not p:
break
if not p.is_dir():
break
inits = [f for f in p.iterdir() if f.name == '__init__.py']
if not inits:
break
paths.append(p.stem)
return '.'.join(reversed(paths))
There are certainly possibilities for improvement, and the optional __init__.py files might necessitate other changes, but if you have __init__.py in general, this does the trick.

Importing classes from different files in a subdirectory

Here's the structure I'm working with:
directory/
script.py
subdir/
__init__.py
myclass01.py
myclass02.py
What I want to do is import in script.py the classes defined in myclass01.py and myclass02.py. If I do:
from subdir.myclass01 import *
It works fine for the class defined in myclass01.py. But with this solution if there are many classes defined in different files in subdir and I want to import all of them, I'd have to type one line for each file. There must be a shortcut for this. I tried:
from subdir.* import *
But it didn't work out.
EDIT: here are the contents of the files:
This is __init__.py (using __all__ as Apalala suggested):
__all__ = ['MyClass01','MyClass02']
This is myclass01.py:
class MyClass01:
def printsomething():
print 'hey'
This is myclass02.py:
class MyClass02:
def printsomething():
print 'sup'
This is script.py:
from subdir import *
MyClass01().printsomething()
MyClass02().printsomething()
This is the traceback that I get when I try to run script.py:
File "script.py", line 1, in <module>
from subdir import *
AttributeError: 'module' object has no attribute 'MyClass01'

Although the names used there are different from what's shown in your question's directory structure, you could use my answer to the question titled Namespacing and classes. The __init__.py shown there would have also allowed the usepackage.py script to have been written this way (package maps to subdir in your question, and Class1 to myclass01, etc):
from package import *
print Class1
print Class2
print Class3
Revision (updated):
Oops, sorry, the code in my other answer doesn't quite do what you want — it only automatically imports the names of any package submodules. To make it also import the named attributes from each submodule requires a few more lines of code. Here's a modified version of the package's __init__.py file (which also works in Python 3.4.1):
def _import_package_files():
""" Dynamically import all the public attributes of the python modules in this
file's directory (the package directory) and return a list of their names.
"""
import os
exports = []
globals_, locals_ = globals(), locals()
package_path = os.path.dirname(__file__)
package_name = os.path.basename(package_path)
for filename in os.listdir(package_path):
modulename, ext = os.path.splitext(filename)
if modulename[0] != '_' and ext in ('.py', '.pyw'):
subpackage = '{}.{}'.format(package_name, modulename) # pkg relative
module = __import__(subpackage, globals_, locals_, [modulename])
modict = module.__dict__
names = (modict['__all__'] if '__all__' in modict else
[name for name in modict if name[0] != '_']) # all public
exports.extend(names)
globals_.update((name, modict[name]) for name in names)
return exports
if __name__ != '__main__':
__all__ = ['__all__'] + _import_package_files() # '__all__' in __all__
Alternatively you can put the above into a separate .py module file of its own in the package directory—such as _import_package_files.py—and use it from the package's __init__.py like this:
if __name__ != '__main__':
from ._import_package_files import * # defines __all__
__all__.remove('__all__') # prevent export (optional)
Whatever you name the file, it should be something that starts with an _ underscore character so it doesn't try to import itself recursively.

Your best option, though probably not the best style, is to import everything into the package's namespace:
# this is subdir/__init__.py
from myclass01 import *
from myclass02 import *
from myclass03 import *
Then, in other modules, you can import what you want directly from the package:
from subdir import Class1

I know it's been a couple months since this question was answered, but I was looking for the same thing and ran across this page. I wasn't very satisfied with the chosen answer, so I ended up writing my own solution and thought I'd share it. Here's what I came up with:
# NOTE: The function name starts with an underscore so it doesn't get deleted by iself
def _load_modules(attr_filter=None):
import os
curdir = os.path.dirname(__file__)
imports = [os.path.splitext(fname)[0] for fname in os.listdir(curdir) if fname.endswith(".py")]
pubattrs = {}
for mod_name in imports:
mod = __import__(mod_name, globals(), locals(), ['*'], -1)
for attr in mod.__dict__:
if not attr.startswith('_') and (not attr_filter or attr_filter(mod_name, attr)):
pubattrs[attr] = getattr(mod, attr)
# Restore the global namespace to it's initial state
for var in globals().copy():
if not var.startswith('_'):
del globals()[var]
# Update the global namespace with the specific items we want
globals().update(pubattrs)
# EXAMPLE: Only load classes that end with "Resource"
_load_modules(attr_filter=lambda mod, attr: True if attr.endswith("Resource") else False)
del _load_modules # Keep the namespace clean
This simply imports * from all .py files in the package directory and then only pulls the public ones into the global namespace. Additionally, it allows a filter if only certain public attributes are desired.

I use this simple way:
add the directory to the system path, then
import module or from module import function1, class1 in that directory.
notice that the module is nothing but the name of your *.py file, without the extension part.
Here is a general example:
import sys
sys.path.append("/path/to/folder/")
import module # in that folder
In your case it could be something like this:
import sys
sys.path.append("subdir/")
import myclass01
# or
from myclass01 import func1, class1, class2 # .. etc

from subdir.* import *
You can not use '*' this way directly after the 'from' statement.
You need explict imports. Please check with the Python documentation on imports and packages.

How can I import a module dynamically given its name as string?

I'm writing a Python application that takes a command as an argument, for example:
$ python myapp.py command1
I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like:
myapp/
__init__.py
commands/
__init__.py
command1.py
command2.py
foo.py
bar.py
So I want the application to find the available command modules at runtime and execute the appropriate one.
Python defines an __import__() function, which takes a string for a module name:
__import__(name, globals=None, locals=None, fromlist=(), level=0)
The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name.
Source: https://docs.python.org/3/library/functions.html#__import__
So currently I have something like:
command = sys.argv[1]
try:
command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"])
except ImportError:
# Display error message
command_module.run()
This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code.
Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added.
See also: How do I import a module given the full path?

With Python older than 2.7/3.1, that's pretty much how you do it.
For newer versions, see importlib.import_module for Python 2 and Python 3.
Or using __import__ you can import a list of modules by doing this:
>>> moduleNames = ['sys', 'os', 're', 'unittest']
>>> moduleNames
['sys', 'os', 're', 'unittest']
>>> modules = map(__import__, moduleNames)
Ripped straight from Dive Into Python.

The recommended way for Python 2.7 and 3.1 and later is to use importlib module:
importlib.import_module(name, package=None)
Import a module. The name argument specifies what module to import in absolute or relative terms (e.g. either pkg.mod or ..mod). If the name is specified in relative terms, then the package argument must be set to the name of the package which is to act as the anchor for resolving the package name (e.g. import_module('..mod', 'pkg.subpkg') will import pkg.mod).
e.g.
my_module = importlib.import_module('os.path')

Note: imp is deprecated since Python 3.4 in favor of importlib
As mentioned the imp module provides you loading functions:
imp.load_source(name, path)
imp.load_compiled(name, path)
I've used these before to perform something similar.
In my case I defined a specific class with defined methods that were required.
Once I loaded the module I would check if the class was in the module, and then create an instance of that class, something like this:
import imp
import os
def load_from_file(filepath):
class_inst = None
expected_class = 'MyClass'
mod_name,file_ext = os.path.splitext(os.path.split(filepath)[-1])
if file_ext.lower() == '.py':
py_mod = imp.load_source(mod_name, filepath)
elif file_ext.lower() == '.pyc':
py_mod = imp.load_compiled(mod_name, filepath)
if hasattr(py_mod, expected_class):
class_inst = getattr(py_mod, expected_class)()
return class_inst

Using importlib
Importing a source file
Here is a slightly adapted example from the documentation:
import sys
import importlib.util
file_path = 'pluginX.py'
module_name = 'pluginX'
spec = importlib.util.spec_from_file_location(module_name, file_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
# Verify contents of the module:
print(dir(module))
From here, module will be a module object representing the pluginX module (the same thing that would be assigned to pluginX by doing import pluginX). Thus, to call e.g. a hello function (with no parameters) defined in pluginX, use module.hello().
To get the effect "importing" functionality from the module instead, store it in the in-memory cache of loaded modules, and then do the corresponding from import:
sys.modules[module_name] = module
from pluginX import hello
hello()
Importing a package
To import a package instead, calling import_module is sufficient. Suppose there is a package folder pluginX in the current working directory; then just do
import importlib
pkg = importlib.import_module('pluginX')
# check if it's all there..
print(dir(pkg))

Use the imp module, or the more direct __import__() function.

You can use exec:
exec("import myapp.commands.%s" % command)

If you want it in your locals:
>>> mod = 'sys'
>>> locals()['my_module'] = __import__(mod)
>>> my_module.version
'2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit (Intel)]'
same would work with globals()

Similar as #monkut 's solution but reusable and error tolerant described here http://stamat.wordpress.com/dynamic-module-import-in-python/:
import os
import imp
def importFromURI(uri, absl):
mod = None
if not absl:
uri = os.path.normpath(os.path.join(os.path.dirname(__file__), uri))
path, fname = os.path.split(uri)
mname, ext = os.path.splitext(fname)
if os.path.exists(os.path.join(path,mname)+'.pyc'):
try:
return imp.load_compiled(mname, uri)
except:
pass
if os.path.exists(os.path.join(path,mname)+'.py'):
try:
return imp.load_source(mname, uri)
except:
pass
return mod

The below piece worked for me:
>>>import imp;
>>>fp, pathname, description = imp.find_module("/home/test_module");
>>>test_module = imp.load_module("test_module", fp, pathname, description);
>>>print test_module.print_hello();
if you want to import in shell-script:
python -c '<above entire code in one line>'

The following worked for me:
import sys, glob
sys.path.append('/home/marc/python/importtest/modus')
fl = glob.glob('modus/*.py')
modulist = []
adapters=[]
for i in range(len(fl)):
fl[i] = fl[i].split('/')[1]
fl[i] = fl[i][0:(len(fl[i])-3)]
modulist.append(getattr(__import__(fl[i]),fl[i]))
adapters.append(modulist[i]())
It loads modules from the folder 'modus'. The modules have a single class with the same name as the module name. E.g. the file modus/modu1.py contains:
class modu1():
def __init__(self):
self.x=1
print self.x
The result is a list of dynamically loaded classes "adapters".