Python：如何从依赖于模块的另一个文件中正确导入函数

Question

Suppose I have two files. The first one contains all the functions I've written and which I usually import from my main file:

# my_functions.py

def sqrt_product(a, b):
    from math import sqrt
    return sqrt(a*b)

def create_df(lst):
    from pandas import DataFrame as df
    return df(lst)

and my main file:

# main.py
from my_functions import sqrt_product, create_df

print(sqrt_product(3, 3))
print(create_df([1, 2, 3])

Is there a more efficient way to import this function? Do I have to import every module for every function I create? WHat if I have several functions in the same file that relies on the same module?

Answer 1

This is how.

 import my_functions as repo

Usage:

repo.sqrt_product(a, b)
repo.create_df(lst)

print(repo.sqrt_product(3, 3))
print(repo.create_df([1, 2, 3])

"repo" is now in the namespace. Just like import pandas as pd , pd is in namespace.

# my_functions.py
from math   import sqrt
from pandas import DataFrame as df
#Or import pandas as pd 

def sqrt_product(a, b):
    return sqrt(a*b)

def create_df(lst):
    return df(lst)
    #return pd.DataFrame(lst)

Answer 2

You can move the from pandas import DataFrame (optionally with as df ) to the top of my_functions.py and redefine create_df just to be:

def create_df(lst):
    return DataFrame(lst)   # or df(lst) if you used as

The create_df function will still work when you import it without requiring you to import anything from pandas . It will be imported with everything it needs to do its thing.

This isn't just true for imported dependencies.

x = 5
def y():
    return x

If you go somewhere else and import y , you will find that y() returns 5, whether or not you imported x . Whatever the function object needs to do its job, it carries with it. This includes when it is imported into another module.

Answer 3

U can do this as well.

# main.py
from my_functions import *

print(sqrt_product(3, 3))
print(create_df([1, 2, 3])

Answer 4

There are a few ways to do this.

1. Import the file from the current directory.

   • make sure the file you are importing from doesn't have any spaces or dashes in its file name. (Ex: thing_to_import_from.py , not thing to import from.py .)

   • make sure both files are in the same directory.

     Import the file and function like so:

      from thing_to_import_from import function_to_import1, function_to_import2 

2. Import the file from another directory.

   • If the file is in a folder or subfolder within the same directory, and the path contains no spaces, it can be imported like so:

      from folder/subfolder/thing_folder/thing_to_import_from import function_to_import 

   • else, add the path to the python sys.path, then import as before.

      import sys sys.path.insert(0, "/folder/subfolder/thing folder") from thing_to_import_from import function_to_import 

3. Make the file into a python module.

   • You should ONLY do this if you intend to use the file with multiple programs for an extended period of time. Don't junk up your Lib folder!

     1. Make a folder in your Lib folder with the desired library name. (The default location of Lib for Python2.7 on Windows is C:\\Python27\\Lib , for example.)
     2. Place your script with the functions to import within this folder.
     3. Create an __init__.py script within this folder. If your script doesn't need any special initialization and doesn't import any other non-library scripts, this can be a blank file.

     4. Import your script as a module!

         from thing_to_import_from import function_to_import