Why script can't find new module after using system command to install package when the script in the running status:
what directory structure looks like:
mymoduledir
|- target_module_dir
|- main.py
main.py code like this:
if __name__ == "__main__":
try:
import target_module
print("module already exist")
# to-do something
except ImportError:
print("has not target_module, start install")
os.system("cd target-module-dir && python setup.py install")
print("install finished")
import target_module
# to-do something
I found that:
if python environment has no target module, my script will auto install it successfully, but I got import error. log display:
has not target_module, start install
running install
.....
Finished processing dependencies for target_module
install finished
Traceback (most recent call last):
File ".\main.py", line 237, in
import target_module
ImportError: No module named target_module_name
It means that the target module was installed successfully, but I met an importerror when I want to import it. To prove my conclusion, I open the python shell and try import the target module, it works. When I rerun this script, log display:
module already exist
It means this script import target module successfully
What I think is:
script will check the python environment before launched, if I want to import an new module in running status of script, I need to let the script know the environment has updated.
What I have try is:
I have searched many related problem, but I haven't got an effective solution.
For some reason, I must use python2.6 to complete my function.And I try to use reload function, like this, but it can't work.
What should I do to solve this problem?
Using pip install will work well, My Solution:
import pip
if __name__ == "__main__":
try:
import target_module
print("module already exist")
# to-do something
except ImportError:
print("has not target_module, start install")
pip.main(['install', './target_module_dir/'])
print("install finished")
import target_module
# to-do something
I want to get a list from all imports of a (selfwritten) module and fetch them via PIP programmatically. Is there a way to do this?
I thought of analysing the file via open(model.py) extract the import statements and then subprocess PIP, but is there a better way?
EDIT:
This helps out with PIP:
http://blog.ducky.io/python/2013/08/22/calling-pip-programmatically/
There are two options that I know of.
pigar
pipreqs
Both will pull imports from your project and give you a requirements.txt file that you can use with pip.
You could wrap it in a try/except condition.
something like:
import pip
while True:
try:
import mymodule
break
except ImportError as e:
dependency = str(e).split(" ")[-1]
if dependency == 'mymodule':
break
pip.main(['install', dependency])
my thinking:
try to import - if you don't have the dependencies installed you should raise an ImportError
if it fails the last word of the error message should be the name of the module you need, install it using pip as suggested in the page you linked.
you could also get an ImportError if your module doesn't exist - so we test for that and break
I can imagine a problem, depending on the pip module (which I haven't used) if a module has a different import name to pip name, eg MySQLdb, which is installed via $pip install MySQL-python
Depending on the answer from Rob, I came to the following solution:
def satisfy_dependencies(path_to_dir):
# Generate requirements.txt using pipreqs and then use pip to fetch the requirements
proc = Popen(["pipreqs", path_to_dir, "--savepath", os.path.join(path_to_dir, "requirements.txt"), "--force"])
while proc.poll() is None:
time.sleep(0.1)
if os.path.exists(os.path.join(path_to_dir, "requirements.txt")):
pip = Popen(["pip", "install", "-r", os.path.join(path_to_dir, "requirements.txt")])
while pip.poll() is None:
time.sleep(0.1)
os.remove(os.path.join(path_to_dir, "requirements.txt"))
Much sub processing but did the job in my case.
I'll be back.
Ive been writing a little script to bootstrap an environment for me, but ran into some confusion when attempting to handle module import errors. My intention was to catch any import error for the yaml module, and then use apt to install the module, and re-import it...
def install_yaml():
print "Attempting to install python-yaml"
print "=============== Begining of Apt Output ==============="
if subprocess.call(["apt-get", "-y", "install", "python-yaml"]) != 0 :
print "Failure whilst installing python-yaml"
sys.exit(1)
print "================= End of Apt Output =================="
#if all has gone to plan attempt to import yaml
import yaml
reload(yaml)
try:
import yaml
except ImportError:
print "Failure whilst importing yaml"
install_yaml()
grains_config = {}
grains_config['bootstrap version'] = __version__
grains_config['bootstrap time'] = "{0}".format(datetime.datetime.now())
with open("/tmp/doc.yaml", 'w+') as grains_file:
yaml.dump(grains_config, grains_file, default_flow_style=False)
Unfortunately when run I get a NameError
Traceback (most recent call last):
File "importtest-fail.py", line 32, in <module>
yaml.dump(grains_config, grains_file, default_flow_style=False)
NameError: name 'yaml' is not defined
After some research I discovered the reload builtin (Reload a previously imported module), which sounded like what I wanted to do, but still results in a NameError on the yaml modules first use.
Does anyone have any suggestions that would allow me to handle the import exception, install the dependencies and "re-import" it?
I could obviously wrap the python script in some bash to do the initial dependency install, but its not a very clean solution.
Thanks
You imported yaml as a local in install_yaml(). You'd have to mark it as a global instead:
global yaml
inside the function, or better still, move the import out of the function and put it right after calling install_yaml().
Personally, I'd never auto-install a dependency this way. Just fail and leave it to the administrator to install the dependency properly. They could be using other means (such as a virtualenv) to manage packages, for example.
What's a good way to check if a package is installed while within a Python script? I know it's easy from the interpreter, but I need to do it within a script.
I guess I could check if there's a directory on the system that's created during the installation, but I feel like there's a better way. I'm trying to make sure the Skype4Py package is installed, and if not I'll install it.
My ideas for accomplishing the check
check for a directory in the typical install path
try to import the package and if an exception is throw, then install package
If you mean a python script, just do something like this:
Python 3.3+ use sys.modules and find_spec:
import importlib.util
import sys
# For illustrative purposes.
name = 'itertools'
if name in sys.modules:
print(f"{name!r} already in sys.modules")
elif (spec := importlib.util.find_spec(name)) is not None:
# If you choose to perform the actual import ...
module = importlib.util.module_from_spec(spec)
sys.modules[name] = module
spec.loader.exec_module(module)
print(f"{name!r} has been imported")
else:
print(f"can't find the {name!r} module")
Python 3:
try:
import mymodule
except ImportError as e:
pass # module doesn't exist, deal with it.
Python 2:
try:
import mymodule
except ImportError, e:
pass # module doesn't exist, deal with it.
As of Python 3.3, you can use the find_spec() method
import importlib.util
# For illustrative purposes.
package_name = 'pandas'
spec = importlib.util.find_spec(package_name)
if spec is None:
print(package_name +" is not installed")
Updated answer
A better way of doing this is:
import subprocess
import sys
reqs = subprocess.check_output([sys.executable, '-m', 'pip', 'freeze'])
installed_packages = [r.decode().split('==')[0] for r in reqs.split()]
The result:
print(installed_packages)
[
"Django",
"six",
"requests",
]
Check if requests is installed:
if 'requests' in installed_packages:
# Do something
Why this way? Sometimes you have app name collisions. Importing from the app namespace doesn't give you the full picture of what's installed on the system.
Note, that proposed solution works:
When using pip to install from PyPI or from any other alternative source (like pip install http://some.site/package-name.zip or any other archive type).
When installing manually using python setup.py install.
When installing from system repositories, like sudo apt install python-requests.
Cases when it might not work:
When installing in development mode, like python setup.py develop.
When installing in development mode, like pip install -e /path/to/package/source/.
Old answer
A better way of doing this is:
import pip
installed_packages = pip.get_installed_distributions()
For pip>=10.x use:
from pip._internal.utils.misc import get_installed_distributions
Why this way? Sometimes you have app name collisions. Importing from the app namespace doesn't give you the full picture of what's installed on the system.
As a result, you get a list of pkg_resources.Distribution objects. See the following as an example:
print installed_packages
[
"Django 1.6.4 (/path-to-your-env/lib/python2.7/site-packages)",
"six 1.6.1 (/path-to-your-env/lib/python2.7/site-packages)",
"requests 2.5.0 (/path-to-your-env/lib/python2.7/site-packages)",
]
Make a list of it:
flat_installed_packages = [package.project_name for package in installed_packages]
[
"Django",
"six",
"requests",
]
Check if requests is installed:
if 'requests' in flat_installed_packages:
# Do something
If you want to have the check from the terminal, you can run
pip3 show package_name
and if nothing is returned, the package is not installed.
If perhaps you want to automate this check, so that for example you can install it if missing, you can have the following in your bash script:
pip3 show package_name 1>/dev/null #pip for Python 2
if [ $? == 0 ]; then
echo "Installed" #Replace with your actions
else
echo "Not Installed" #Replace with your actions, 'pip3 install --upgrade package_name' ?
fi
Open your command prompt type
pip3 list
As an extension of this answer:
For Python 2.*, pip show <package_name> will perform the same task.
For example pip show numpy will return the following or alike:
Name: numpy
Version: 1.11.1
Summary: NumPy: array processing for numbers, strings, records, and objects.
Home-page: http://www.numpy.org
Author: NumPy Developers
Author-email: numpy-discussion#scipy.org
License: BSD
Location: /home/***/anaconda2/lib/python2.7/site-packages
Requires:
Required-by: smop, pandas, tables, spectrum, seaborn, patsy, odo, numpy-stl, numba, nfft, netCDF4, MDAnalysis, matplotlib, h5py, GridDataFormats, dynd, datashape, Bottleneck, blaze, astropy
In the Terminal type
pip show some_package_name
Example
pip show matplotlib
You can use the pkg_resources module from setuptools. For example:
import pkg_resources
package_name = 'cool_package'
try:
cool_package_dist_info = pkg_resources.get_distribution(package_name)
except pkg_resources.DistributionNotFound:
print('{} not installed'.format(package_name))
else:
print(cool_package_dist_info)
Note that there is a difference between python module and a python package. A package can contain multiple modules and module's names might not match the package name.
if pip list | grep -q \^'PACKAGENAME\s'
# installed ...
else
# not installed ...
fi
You can use this:
class myError(exception):
pass # Or do some thing like this.
try:
import mymodule
except ImportError as e:
raise myError("error was occurred")
Method 1
to search weather a package exists or not use pip3 list command
#**pip3 list** will display all the packages and **grep** command will search for a particular package
pip3 list | grep your_package_name_here
Method 2
You can use ImportError
try:
import your_package_name
except ImportError as error:
print(error,':( not found')
Method 3
!pip install your_package_name
import your_package_name
...
...
I'd like to add some thoughts/findings of mine to this topic.
I'm writing a script that checks all requirements for a custom made program. There are many checks with python modules too.
There's a little issue with the
try:
import ..
except:
..
solution.
In my case one of the python modules called python-nmap, but you import it with import nmap and as you see the names mismatch. Therefore the test with the above solution returns a False result, and it also imports the module on hit, but maybe no need to use a lot of memory for a simple test/check.
I also found that
import pip
installed_packages = pip.get_installed_distributions()
installed_packages will have only the packages has been installed with pip.
On my system pip freeze returns over 40 python modules, while installed_packages has only 1, the one I installed manually (python-nmap).
Another solution below that I know it may not relevant to the question, but I think it's a good practice to keep the test function separate from the one that performs the install it might be useful for some.
The solution that worked for me. It based on this answer How to check if a python module exists without importing it
from imp import find_module
def checkPythonmod(mod):
try:
op = find_module(mod)
return True
except ImportError:
return False
NOTE: this solution can't find the module by the name python-nmap too, I have to use nmap instead (easy to live with) but in this case the module won't be loaded to the memory whatsoever.
I would like to comment to #ice.nicer reply but I cannot, so ...
My observations is that packages with dashes are saved with underscores, not only with dots as pointed out by #dwich comment
For example, you do pip3 install sphinx-rtd-theme, but:
importlib.util.find_spec(sphinx_rtd_theme) returns an Object
importlib.util.find_spec(sphinx-rtd-theme) returns None
importlib.util.find_spec(sphinx.rtd.theme) raises ModuleNotFoundError
Moreover, some names are totally changed.
For example, you do pip3 install pyyaml but it is saved simply as yaml
I am using python3.8
If you'd like your script to install missing packages and continue, you could do something like this (on example of 'krbV' module in 'python-krbV' package):
import pip
import sys
for m, pkg in [('krbV', 'python-krbV')]:
try:
setattr(sys.modules[__name__], m, __import__(m))
except ImportError:
pip.main(['install', pkg])
setattr(sys.modules[__name__], m, __import__(m))
A quick way is to use python command line tool.
Simply type import <your module name>
You see an error if module is missing.
$ python
Python 2.7.6 (default, Jun 22 2015, 17:58:13)
>>> import sys
>>> import jocker
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named jocker
$
Hmmm ... the closest I saw to a convenient answer was using the command line to try the import. But I prefer to even avoid that.
How about 'pip freeze | grep pkgname'? I tried it and it works well. It also shows you the version it has and whether it is installed under version control (install) or editable (develop).
I've always used pylibcheck to check if a lib is installed or not, simply download it by doing pip install pylibcheck and the could could be like this
import pylibcheck
if not pylibcheck.checkPackage("mypackage"):
#not installed
it also supports tuples and lists so you can check multiple packages and if they are installed or not
import pylibcheck
packages = ["package1", "package2", "package3"]
if pylibcheck.checkPackage(packages):
#not installed
you can also install libs with it if you want to do that, recommend you check the official pypi
The top voted solution which uses techniques like importlib.util.find_spec and sys.modules and catching import exceptions works for most packages but fails in some edge cases (such as the beautifulsoup package) where the package name used in imports is somewhat different (bs4 in this case) than the one used in setup file configuration. For these edge cases, this solution doesn't work unless you pass the package name used in imports instead of the one used in requirements.txt or pip installations.
For my use case, I needed to write a package checker that checks installed packages based on requirements.txt, so this solution didn't work. What I ended up using was subprocess.check to call the pip module explicitly to check for the package installation:
import subprocess
for pkg in packages:
try:
subprocess.check_output('py -m pip show ' + pkg)
except subprocess.CalledProcessError as ex:
not_found.append(pkg)
It's a bit slower than the other methods but more reliable and handles the edge cases.
Go option #2. If ImportError is thrown, then the package is not installed (or not in sys.path).
Is there any chance to use the snippets given below? When I run this code, it returns "module pandas is not installed"
a = "pandas"
try:
import a
print("module ",a," is installed")
except ModuleNotFoundError:
print("module ",a," is not installed")
But when I run the code given below:
try:
import pandas
print("module is installed")
except ModuleNotFoundError:
print("module is not installed")
It returns "module pandas is installed".
What is the difference between them?