从Python中的另一个文件调用函数

Set_up: I have a .py file for each function I need to use in a program.

In this program, I need to call the function from the external files.

I’ve tried:

from file.py import function(a,b)

But I get the error:

ImportError: No module named ‘file.py’; file is not a package

How do I fix this problem?

There isn’t any need to add file.py while importing. Just write from file import function, and then call the function using function(a, b). The reason why this may not work, is because file is one of Python’s core modules, so I suggest you change the name of your file.

Note that if you’re trying to import functions from a.py to a file called b.py, you will need to make sure that a.py and b.py are in the same directory.

First of all you do not need a .py.

If you have a file a.py and inside you have some functions:

def b():
  # Something
  return 1

def c():
  # Something
  return 2

And you want to import them in z.py you have to write

from a import b, c

You can do this in 2 ways. First is just to import the specific function you want from file.py. To do this use

from file import function

Another way is to import the entire file

import file as fl

Then you can call any function inside file.py using

fl.function(a,b)

You can call the function from a different directory as well, in case you cannot or do not want to have the function in the same directory you are working. You can do this in two ways (perhaps there are more alternatives, but these are the ones that have worked for me).

Alternative 1 Temporarily change your working directory

import os

os.chdir("**Put here the directory where you have the file with your function**")

from file import function

os.chdir("**Put here the directory where you were working**")

Alternative 2 Add the directory where you have your function to sys.path

import sys

sys.path.append("**Put here the directory where you have the file with your function**")

from file import function

If your file is in the different package structure and you want to call it from a different package, then you can call it in that fashion:

Let’s say you have following package structure in your python project:

in – com.my.func.DifferentFunction python file you have some function, like:

def add(arg1, arg2):
    return arg1 + arg2

def sub(arg1, arg2) :
    return arg1 - arg2

def mul(arg1, arg2) :
    return arg1 * arg2

And you want to call different functions from Example3.py, then following way you can do it:

Define import statement in Example3.py – file for import all function

from com.my.func.DifferentFunction import *

or define each function name which you want to import

from com.my.func.DifferentFunction import add, sub, mul

Then in Example3.py you can call function for execute:

num1 = 20
num2 = 10

print("\n add : ", add(num1,num2))
print("\n sub : ", sub(num1,num2))
print("\n mul : ", mul(num1,num2))

Output:

 add :  30

 sub :  10

 mul :  200

Came across the same feature but I had to do the below to make it work.

If you are seeing ‘ModuleNotFoundError: No module named’, you probably need the dot(.) in front of the filename as below;

from .file import funtion

First save the file in .py format (for example, my_example.py). And if that file have functions,

def xyz():

        --------

        --------

def abc():

        --------

        --------

In the calling function you just have to type the below lines.

file_name: my_example2.py

============================

import my_example.py


a = my_example.xyz()

b = my_example.abc()

============================

Rename the module to something other than ‘file’.

Then also be sure when you are calling the function that:

1)if you are importing the entire module, you reiterate the module name when calling it:

import module
module.function_name()

or

import pizza
pizza.pizza_function()

2)or if you are importing specific functions, functions with an alias, or all functions using *, you don’t reiterate the module name:

from pizza import pizza_function
pizza_function()

or

from pizza import pizza_function as pf
pf()

or

from pizza import *
pizza_function()

Functions from .py file (can (of course) be in different directory) can be simply imported by writing directories first and then the file name without .py extension:

from directory_name.file_name import function_name

And later be used: function_name()

Inside MathMethod.Py.

def Add(a,b):
   return a+b 

def subtract(a,b):
  return a-b

Inside Main.Py

import MathMethod as MM 
  print(MM.Add(200,1000))

Output:1200

You don’t have to add file.py.

Just keep the file in the same location with the file from where you want to import it. Then just import your functions:

from file import a, b

You should have the file at the same location as that of the Python files you are trying to import. Also ‘from file import function’ is enough.

append a dot(.) in front of a file name if you want to import this file which is in the same directory where you are running your code.

For example, i’m running a file named a.py and i want to import a method named addFun which is written in b.py, and b.py is there in the same directory

from .b import addFun

Suppose the file you want to call is anotherfile.py and the method you want to call is method1, then first import the file and then the method

from anotherfile import method1

if method1 is part of a class, let the class be class1, then

from anotherfile import class1

then create an object of class1, suppose the object name is ob1, then

ob1 = class1()
ob1.method1()

in my case i named my file helper.scrap.py and couldn’t make it work until i changed to helper.py