your “library” code

tjohnson · July 21, 2015, 10:30pm

import(module) cannot be used as a drop-in replacement for import module, because it returns the imported module rather than initializing it as a variable. This link may be helpful: http://effbot.org/zone/import-string.htm

There are several alternatives to using the import statement or the import() function:

You can use exec(), which is probably undesirable.
You can use the imp module.
You can use the importlib module (as Werner suggested).
These links may also be helpful:

···

On Tuesday, July 21, 2015 at 1:54:22 PM UTC-4, Boštjan Mejak wrote:

def tryToImport(module):

try:

import module

except ImportError:

print(“The import failed.”)

As you can see from my code above, the function tryToImport() takes a ‘module’ argument which is then taken as a module to be imported. But I always get “The import failed.” message. Why does my code not work? No module can be imported this way, even the built-in Python modules. How can I refactor my code to make this work?

tjohnson · July 22, 2015, 11:15am

I understand your problem. All of the Python functions that import modules (import, importlib.import_module, and imp.load_source) will only return the module as an object. They will NOT add it to the global namespace. Try using this code for your function (obtained from this StackOverflow answer):

def tryToImport(module):
try:
globals()[module] = import(module)
except:
print(“The import failed.”)

···

On Wednesday, July 22, 2015 at 6:22:41 AM UTC-4, Boštjan Mejak wrote:

def tryToImport(module):

try:

import importlib

importlib.import_module(module)

except ImportError:

print(“The import failed.”)

Try to create the exact same function, as is above, in your interpreter and then do this:

tryToImport(“wx”)

You will notice that everything went smoothly, until you do this:

wx

Now what the hell is this? A NameError I get? But I just imported wx with no errors. Well, my friend, that’s my hell that I am going through.

Tim_Roberts · July 22, 2015, 7:59pm

Days? Seriously? Consider this:
That fails in exactly the same way for exactly the same reason. Can
you see why?

···

Boštjan Mejak wrote:

Your code doesn’t work. Try importing sys
using your code in the interactive interpreter and then type sys and
hit Enter. You’ll get a NameError as if sys wasn’t
imported at all.

I’m struggling with this for days now.

` def one():``

``        x = 3``

``    ``

``    ``one()``

``    print( x )``

`

-- Tim Roberts, Providenza & Boekelheide, Inc.

timr@probo.com

Cody · July 22, 2015, 8:00pm

Hi,

Not sure why you want to try and conditionally import the sys module. It will always exist never going to fail. Anyway your problem just appears to be a fundamental misunderstanding of between what a variable is and the value that is assigned to the variable…

The import functions return an instance of the module object, this instance not automatically bound to a name in the global namespace like is done when using the normal import keyword statement.

Also unlike the “import” statement ( import foo) the import function takes a string as an argument not an unbound variable ( import_module(“moduleName”) vs import moduleName ) the later keyword statement has special hook that calls the import function and then assigns the loaded object to the named variable in the global namespace.

You, probably would have been able to catch this mistake in your earlier attempts if you had actually looked at the message in the exception that was generated as it would have have said something an failed to import “module” where “module” was literally the name of the module it tried to import and not the value of the string variable you had passed in.

Output from interactive session:

First note that import_module returns the module as a local variable (I assigned the “sys” module to variable ‘x’)
dir shows that it is the contents of the sys module
Then assign x to “sys” in globals, there will now be a global “sys” variable that references the sys module
dir(sys) now shows that the global “sys” is the sys module

Python 2.7.9 (default, Dec 10 2014, 12:24:55) [MSC v.1500 32 bit (Intel)] on win

32

Type “help”, “copyright”, “credits” or “license” for more information.

import importlib

x = importlib.import_module(“sys”)

dir(x)

[‘displayhook’, ‘doc’, ‘excepthook’, ‘name’, ‘package’, '__s

tderr__', ‘stdin’, ‘stdout’, ‘_clear_type_cache’, ‘_current_frames’, '_g

etframe’, ‘_mercurial’, ‘api_version’, ‘argv’, ‘builtin_module_names’, 'byteorde

r’, ‘call_tracing’, ‘callstats’, ‘copyright’, ‘displayhook’, ‘dllhandle’, 'dont_

write_bytecode’, ‘exc_clear’, ‘exc_info’, ‘exc_type’, ‘excepthook’, 'exec_prefix

', ‘executable’, ‘exit’, ‘flags’, ‘float_info’, ‘float_repr_style’, 'getcheckint

erval’, ‘getdefaultencoding’, ‘getfilesystemencoding’, ‘getprofile’, 'getrecursi

onlimit’, ‘getrefcount’, ‘getsizeof’, ‘gettrace’, ‘getwindowsversion’, 'hexversi

on’, ‘long_info’, ‘maxint’, ‘maxsize’, ‘maxunicode’, ‘meta_path’, ‘modules’, 'pa

th’, ‘path_hooks’, ‘path_importer_cache’, ‘platform’, ‘prefix’, ‘ps1’, ‘ps2’, 'p

y3kwarning’, ‘setcheckinterval’, ‘setprofile’, ‘setrecursionlimit’, ‘settrace’,

‘stderr’, ‘stdin’, ‘stdout’, ‘subversion’, ‘version’, ‘version_info’, 'warnoptio

ns’, ‘winver’]

globals()[“sys”] = x

dir(sys)