I am trying to import a module from inside a function and have it be available to my whole file the same way it would be if I imported outside any functions and before all the other code. The reason it is in a function is because I don't have much control over the structure of the script. Is this possible without resorting to things like hacking __builtin__ or passing what I need all around my code?
Importing inside a function will effectively import the module once.. the first time the function is run. It ought to import just as fast whether you import it at the top, or when the function is run.
Globals in Python are global to a module, not across all modules. (Unlike C, where a global is the same across all implementation files unless you explicitly make it static.). If you need truly global variables from imported modules, you can set those at an attribute of the module where you're importing it.
__import__() Parameters name - the name of the module you want to import. globals and locals - determines how to interpret name. fromlist - objects or submodules that should be imported by name. level - specifies whether to use absolute or relative imports.
Global (or module) scope is the top-most scope in a Python program, script, or module. This Python scope contains all of the names that you define at the top level of a program or a module. Names in this Python scope are visible from everywhere in your code.
How about something like globals()["os"] = __import__("os")?
I guess this could be wrapped in a generic function if you wanted since the module name is a string.
Seeing your new comments, I want to emphasize that this sounds unnecessary. You're actually modifying the script more by importing within a function than by importing at the top of the script in the normal way. Still, in the spirit of answering the question asked, I'm leaving my previous answer.
I'm honestly not certain this is the correct way to do this, but a quick check confirms that if you declare the module name as global
within the function before importing, it is imported into the global namespace.
>>> def import_re():
... global re
... import re
...
>>> re
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 're' is not defined
>>> import_re()
>>> re
<module 're' from '/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/re.pyc'>
Don't do this unless you really have to -- and then write it in big red letters, so to speak.
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