How to import a module given its name as string

Question

I m writing a Python application that takes as 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

User · Answer

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

User · Answer

You can use exec   exec  import myapp commands  s    command

User · Answer

Use the imp module  or the more direct   import     function

User · Answer

You can use exec   exec  import myapp commands  s    command

User · Answer

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

User · Answer

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

User · Answer

For example  my module names are like jan module feb module mar module   month    feb  exec  from  s module import     month

User · Answer

The below piece worked for me    gt  gt  gt import imp    gt  gt  gt fp  pathname  description   imp find module   home test module      gt  gt  gt test module   imp load module  test module   fp  pathname  description    gt  gt  gt print test module print hello      if you want to import in shell-script   python -c   lt above entire code in one line gt

User · Answer

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 and Python 3   You can use exec if you want to as well   Or using   import   you can import a list of modules by doing this    gt  gt  gt  moduleNames     sys    os    re    unittest     gt  gt  gt  moduleNames   sys    os    re    unittest    gt  gt  gt  modules   map   import    moduleNames    Ripped straight from Dive Into Python

User · Answer

If you want it in your locals    gt  gt  gt  mod    sys   gt  gt  gt  locals    my module       import   mod   gt  gt  gt  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

User · Answer

Nowadays you should use importlib    Import a source file  The docs actually provide a recipe for that  and it goes like   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     check if it s all there   def bla mod       print dir mod   bla module    This way you can access the members  e g  a function  hello   from your module pluginX py -- in this snippet being called module -- under its namespace  E g  module hello     If you want to import the members  e g   hello   you can include module pluginX in the in-memory list of modules   sys modules module name    module  from pluginX import hello hello     Import a package  Importing a package  e g   pluginX   init   py  under your current dir is actually straightforward   import importlib  pkg   importlib import module  pluginX      check if it s all there   def bla mod       print dir mod   bla pkg

User · Answer

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

User · Answer

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

User · Answer

Use the imp module  or the more direct   import     function

User · Answer

The below piece worked for me    gt  gt  gt import imp    gt  gt  gt fp  pathname  description   imp find module   home test module      gt  gt  gt test module   imp load module  test module   fp  pathname  description    gt  gt  gt print test module print hello      if you want to import in shell-script   python -c   lt above entire code in one line gt

User · Answer

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

User · Answer

Nowadays you should use importlib    Import a source file  The docs actually provide a recipe for that  and it goes like   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     check if it s all there   def bla mod       print dir mod   bla module    This way you can access the members  e g  a function  hello   from your module pluginX py -- in this snippet being called module -- under its namespace  E g  module hello     If you want to import the members  e g   hello   you can include module pluginX in the in-memory list of modules   sys modules module name    module  from pluginX import hello hello     Import a package  Importing a package  e g   pluginX   init   py  under your current dir is actually straightforward   import importlib  pkg   importlib import module  pluginX      check if it s all there   def bla mod       print dir mod   bla pkg

User · Answer

You can use exec   exec  import myapp commands  s    command

User · Answer

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

User · Answer

For example  my module names are like jan module feb module mar module   month    feb  exec  from  s module import     month

User · Answer

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

User · Answer

Use the imp module  or the more direct   import     function

User · Answer

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 and Python 3   You can use exec if you want to as well   Or using   import   you can import a list of modules by doing this    gt  gt  gt  moduleNames     sys    os    re    unittest     gt  gt  gt  moduleNames   sys    os    re    unittest    gt  gt  gt  modules   map   import    moduleNames    Ripped straight from Dive Into Python

User · Answer

Use the imp module  or the more direct   import     function

User · Answer

You can use exec   exec  import myapp commands  s    command

User · Answer

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

User · Answer

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

User · Answer

If you want it in your locals    gt  gt  gt  mod    sys   gt  gt  gt  locals    my module       import   mod   gt  gt  gt  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

User · Answer

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 and Python 3   You can use exec if you want to as well   Or using   import   you can import a list of modules by doing this    gt  gt  gt  moduleNames     sys    os    re    unittest     gt  gt  gt  moduleNames   sys    os    re    unittest    gt  gt  gt  modules   map   import    moduleNames    Ripped straight from Dive Into Python

User · Answer

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 and Python 3   You can use exec if you want to as well   Or using   import   you can import a list of modules by doing this    gt  gt  gt  moduleNames     sys    os    re    unittest     gt  gt  gt  moduleNames   sys    os    re    unittest    gt  gt  gt  modules   map   import    moduleNames    Ripped straight from Dive Into Python

[python] How to import a module given its name as string?

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