我应该怎么做才能导入不是stdlib的math.py

Question

I read the docs from python.org, but is still confused about this problem. In one project, I have the following script structure:

dir a:

    math.py containing func c()
    main.py containing main()

What should I do in main.py in order to import math under dir a rather than stdlib?

import math just does not work

Answer 1

Edit:

Sorry my mistake... This will never work. You can choose either to give your top level package a name that doesn't conflicts with a name in the standard library. Or the main script cannot be in the package directory. So basically you can either:

Rename your module to my_math.py and then main.py can be in the same directory and you can just do:

from my_math import c
c()

Or you make a package, for example folder name test (or any other name that doesn't conflict with a standard library package) with files: __init__.py and math.py , and in the same level as the test you create a main.py and then the code will look like:

from test.math import c
c()

Folder structure:

.
|-- test
|   |-- __init__.py
|   `-- math.py
`-- main.py

Answer 2

This CAN work.

sys.path.insert(0,'path/to/math.py')
import math

This will make python check at the specified directory BEFORE stdlibs. This is a risky method for the same reason. I would recommend putting math.py in its OWN directory and using that path, so nothing else is changed.

I would also recommend importing this LAST if you have other modules imported as well.

import stuff
import morestuff
sys.path.insert(0,'path/to/math')
import math

Again, using "math" is not recommended. Renaming is best, especially for popular modules like "math".

Answer 3

You can import modules with exact specification of the path to the module file, and by giving the module a specific name. Have a look at the imp module.

Here's an example:

# file: math.py
def say_hello():
    print "Hello!"

and the main file:

# file: main.py
import imp
my_math = imp.load_source("my_math", "math.py")
my_math.say_hello()

given both files lie where the current working directory is, this works for me.

Note that this approach tends to be highly unmaintainable and unflexible. It is generally a good thing not to clash with standard library and other language feature names. Therefore, you should rename that module or move it to a (non-global) namespace, ie, a subpackage.

For reference:

• http://docs.python.org/2/library/imp.html#imp.load_source
• http://docs.python.org/2/tutorial/modules.html#packages