How to check if a python module exists without importing it

Question

I need to know if a python module exists  without importing it   Importing something that might not exist  not what I want    try      import eggs except ImportError      pass

User · Answer

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

User · Answer

There is no 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 Python module exists    Below solution address the problem that imported module can raise ImportError even it exists  We want to distinguish that situation from such in which 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

User · Answer

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 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 info on the ModuleNotFoundError

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I came across this question while searching for a way to check if a module is loaded from the command line  and would like to share my thoughts for the ones coming after me and looking for the same     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     gt  gt  gt  help  module name     If found quit reading by typing q To exit the python 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 unknown module     python module help py lkajshdflkahsodf   Would output        no Python documentation found for  lkajshdflkahsodf    and exit

User · Answer

A simpler if statement from AskUbuntu  How do I check whether a module is installed in Python   import sys print  eggs  in sys modules

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After use yarbelk s response  I ve made this for don t have to import   mp   try        import    imp   find module  eggs         Make things with supposed existing module except ImportError      pass   Useful in Django s settings pyfor example

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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       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

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go as s answer as a one liner   python -c  help  modules       grep module

User · Answer

I wrote this helper function   def is module available module name       if sys version info  lt   3  0             python 2         import importlib         torch loader   importlib find loader module name      elif sys version info  lt    3  3             python 3 0 to 3 3         import pkgutil         torch loader   pkgutil find loader module name      elif sys version info  gt    3  4             python 3 4 and above         import importlib         torch loader   importlib util find spec module name       return torch loader is not None

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You can also use importlib directly   import importlib  try      importlib import module module name  except ImportError        Handle error

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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

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Python 2  without relying 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 existant 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

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Python2 To check if import can find something in python2  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 python3 part import pkgutil eggs loader   pkgutil find loader  eggs   found   eggs loader is not None  Python3 Python3   3 3 You should use importlib  How I went about doing this was  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   Python3   3 4 In Python3 4 importlib find loader python docs 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  quot spam quot   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  quot   spam quot   package  quot eggs bar quot   found   spam spec is not None spam spec name     quot eggs spam quot   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  quot module food loaded quot       eggs py print  quot module eggs quot    were you then to run  gt  gt  gt  import importlib  gt  gt  gt  spam spec   importlib find spec  quot food eggs quot   module food loaded ModuleSpec name  food eggs   loader  lt  frozen importlib SourceFileLoader object at 0x10221df28 gt   origin   home user food eggs py    comments welcome on getting around this Acknowledgements   rvighne for importlib  lucas-guido for python3 3  depricating find loader  enpenax for pkgutils find loader behaviour in python2 7

[python] How to check if a python module exists without importing it

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