Importing a function from a class in another file?

问题:

I'm writing a Python program for fun but got stuck trying to import a function from a class in another file. Here is my code:

#jurassic park mainframe

from random import randint
from sys import exit
from comm_system import Comm_system #the file i want to import from



class Jpark_mainframe(object):
    def mainframe_home(self):
    print "=====Welcome to the Jurassic Park Mainframe====="
    print "==========Security Administration==============="
    print "===========Communications Systems==============="
    print "===============System Settings=================="
    print "===================Quit========================="

    prompt = raw_input("What would you like to do? ")

    while prompt != "Quit":

        if prompt == "Security Administration":
            print "Please enter the 5-digit passcode:"
            security_passcode = "%d%d%d%d%d" % (2, 0, 1, 2, randint(1, 2))
            security_guess = raw_input(": ")
            security_guesses = 0

            while security_guess != security_passcode and security_guesses < 7:
                print "Incorrect. Please enter the security passcode."
                security_guesses += 1
                security_guess = raw_input(": ")

                if security_guess == security_passcode:
                    print "=========Security Administration======="
                    print "Area 1 Fences: Off"
                    print "Area 2 Fences: On"
                    print "Area 3 Fences: Off"
                    print "Velociraptor Compound: Off"
                    print "Lobby Security System: Off"
                    print "Entrance Facility System: Off"
                    print "To enable all systems, enter 'On'"


                    enable_security = raw_input(": ")

                    if enable_security == "On":
                        print "Systems Online."


        if prompt == "System Settings":
            print "You do not have access to system settings."
            exit(0)


        if prompt == "Communications Systems":
            print "===========Communications Systems==========="
            print "error: 'comm_link' missing in directories"
            exit(0)
            return Comm_system.run #this is where I want to return the 
                                                   #the other file

the_game = jpark_mainframe()
the_game.mainframe_home()

I want to return a function called run() from a class in another file. When I import the file, it first runs the class with run() in it, then proceeds to run the original code. Why does this happen?

Here is the code from comm_system:

#communication systems


from sys import exit

class Comm_system(object):
def run(self):

    comm_directory = ["net_link", "tsfa_run", "j_link"]
    print "When the system rebooted, some files necessary for"
    print "communicating with the mainland got lost in the directory."
    print "The files were poorly labeled as a result of sloppy"
    print "programming on the staff's part. You must locate the"
    print "the file and contact the rescue team before the dinosaurs"
    print "surround the visitor's center. You were also notified the"
    print "generators were shorting out, and the mainframe will lose"
    print "power at any moment. Which directory will you search in?"
    print "you don't have much time! Option 1: cd /comm_sys/file"
    print "Option 2: cd /comm_sys/dis"
    print "Option 3: cd /comm_sys/comm"

    dir_choice = raw_input("jpark_edwin$ ")

    if dir_choice == "/comm_sys/file" or dir_choice == "/comm_sys/dis":
        print "misc.txt" 
        print "You couldn't locate the file!"
        print "The system lost power and your computer shut down on you!"
        print "You will not be able to reach the mainland until the system"
        print "comes back online, and it will be too late by then."
        return 'death'

    if dir_choice == "/comm_sys/comm":
        comm_directory.append("comm_link")
        print comm_directory
        print "You found the right file and activated it!"
        print "Just in time too, because the computers shut down on you."
        print "The phonelines are radios are still online."
        print "You and the other survivors quickly call the mainlane"
        print "and help is on the way. You all run to the roof and wait"
        print "until the helocopter picks you up. You win!"
a_game = Comm_system()
a_game.run()

回答1:

from otherfile import TheClass
theclass = TheClass()
# if you want to return the output of run
return theclass.run()  
# if you want to return run itself to be used later
return theclass.run

Change the end of comm system to:

if __name__ == '__main__':
    a_game = Comm_system()
    a_game.run()

It's those lines being always run that are causing it to be run when imported as well as when executed.

回答2:

from FOLDER_NAME import FILENAME
from FILENAME import CLASS_NAME FUNCTION_NAME

FILENAME is w/o the suffix

回答3:

If, like me, you want to make a function pack or something that people can download then it's very simple. Just write your function in a python file and save it as the name you want IN YOUR PYTHON DIRECTORY. Now, in your script where you want to use this, you type:

from FILE NAME import FUNCTION NAME

Note - the parts in capital letters are where you type the file name and function name.

Now you just use your function however it was meant to be.

Example:

FUNCTION SCRIPT - saved at C:\Python27 as function_choose.py

def choose(a):
  from random import randint
  b = randint(0, len(a) - 1)
  c = a[b]
  return(c)

SCRIPT USING FUNCTION - saved wherever

from function_choose import choose
list_a = ["dog", "cat", "chicken"]
print(choose(list_a))

OUTPUT WILL BE DOG, CAT, OR CHICKEN

Hoped this helped, now you can create function packs for download!

--------------------------------This is for Python 2.7-------------------------------------

回答4:

First you need to make sure if both of your files are in the same working directory. Next, you can import the whole file. For example,

import myClass

or you can import the entire class and entire functions from the file. For example,

from myClass import

Finally, you need to create an instance of the class from the original file and call the instance objects.

回答5:

It would really help if you'd include the code that's not working (from the 'other' file), but I suspect you could do what you want with a healthy dose of the 'eval' function.

For example:

def run():
    print "this does nothing"

def chooser():
    return "run"

def main():
    '''works just like:
    run()'''
    eval(chooser())()

The chooser returns the name of the function to execute, eval then turns a string into actual code to be executed in-place, and the parentheses finish off the function call.

回答6:

You can use the below syntax -

from FolderName.FileName import Classname