import module from string variable

Question

I m working on a documentation  personal  for nested matplotlib  MPL  library  which differs from MPL own provided  by interested submodule packages  I m writing Python script which I hope will automate document generation from future MPL releases  I selected interested submodules packages and want to list their main classes from which I ll generate list and process it with pydoc    Problem is that I can t find a way to instruct Python to load submodule from string  Here is example of what I tried   import matplotlib text as text x   dir text         i     import    matplotlib text   y   dir i       j     import    matplotlib   z   dir j    And here is 3 way comparison of above lists through pprint     I don t understand what s loaded in y object - it s base matplotlib plus something else  but it lack information that I wanted and that is main classes from matplotlib text package  It s top blue coloured part on screenshot  x list   Please don t suggest Sphinx as different approach

User · Answer

I developed these 3 useful functions   def loadModule moduleName       module   None     try          import sys         del sys modules moduleName      except BaseException as err          pass     try          import importlib         module   importlib import module moduleName      except BaseException as err          serr   str err          print  Error to load the module      moduleName           serr      return module  def reloadModule moduleName       module   loadModule moduleName      moduleName  modulePath   str module  replace    from           replace   lt module         replace    gt        split           if  modulePath endswith   pyc             import os         os remove modulePath          module   loadModule moduleName      return module  def getInstance moduleName  param1  param2  param3       module   reloadModule moduleName      instance   eval  module     moduleName     param1  param2  param3        return instance   And everytime I want to reload a new instance I just have to call getInstance   like this   myInstance   getInstance  MyModule   myParam1  myParam2  myParam3    Finally I can call all the functions inside the new Instance   myInstance aFunction     The only specificity here is to customize the params list  param1  param2  param3  of your instance

User · Answer

The   import   function can be a bit hard to understand   If you change   i     import    matplotlib text     to  i     import    matplotlib text   fromlist         then i will refer to matplotlib text   In Python 2 7 and Python 3 1 or later  you can use importlib   import importlib  i   importlib import module  matplotlib text     Some notes   If you re trying to import something from a sub-folder e g    feature email py  the code will look like importlib import module  feature email   You can t import anything if there is no   init   py in the folder with file you are trying to import

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Apart from using the importlib one can also use exec method to import a module from a string variable   Here I am showing an example of importing the combinations method from itertools package using the exec method   MODULES           itertools   combinations       for ITEM in MODULES      import str    from  0  import  1   format ITEM 0       join str i  for i in ITEM 1         exec import str   ar   list combinations  1  2  3  4   2   for elements in ar      print elements    Output    1  2   1  3   1  4   2  3   2  4   3  4

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spent some time trying to import modules from a list  and this is the thread that got me most of the way there - but I didnt grasp the use of    import     -   so here s how to import a module from a string  and get the same behavior as just import   And try except the error case  too        pipmodules     pycurl    ansible    bad module no beer     for module in pipmodules        try              because we want to import using a variable  do it this way           module obj     import   module              create a global object containging our module           globals   module    module obj       except ImportError            sys stderr write  ERROR  missing python module      module     n             sys exit 1    and yes  for python 2 7  you have other options - but for 2 6 lt   this works

User · Answer

importlib import module is what you are looking for  It returns the imported module   Only available for Python    2 7 or 3 x    import importlib  mymodule   importlib import module  matplotlib text     You can thereafter access anything in the module as mymodule myclass  etc

[python] import module from string variable

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