How to share variable between functions in python?

问题

I have 2 functions fun1 and fun2 which take as inputs a string and a number respectively. The also both get as input the same variable a. This is the code:

a = ['A','X','R','N','L']

def fun1(string,vect):
    out = []
    for letter in vect:
        out. append(string+letter)
    return out

def fun2(number,vect):
    out = []
    for letter in vect:
        out.append(str(number)+letter)
    return out

x = fun1('Hello ',a)
y = fun2(2,a)

The functions perform some nonsense operations. My goal would be to rewrite the code in such a way that the variable a is shared between the functions so that they do not take it as input anymore.

One way to remove variable a as input would be by defining it within the functions themselves but unfortunately that is not very elegant. Could you suggest me a possible way to reach my goal?

The functions should operate in the same way but the input arguments should only be the string and the number (fun1(string), fun2(number)).

回答1:

Object-oriented programming helps here:

class MyClass(object):
    def __init__(self):
        self.a = ['A','X','R','N','L']  # Shared instance member :D

    def fun1(self, string):
        out = []
        for letter in self.a:
            out.append(string+letter)
        return out

    def fun2(self, number):
        out = []
        for letter in self.a:
            out.append(str(number)+letter)
        return out

a = MyClass()
x = a.fun1('Hello ')
y = a.fun2(2)

回答2:

An alternative to using classes: You can use the global keyword to use variables that lie outside the function.

a = 5
def func():
    global a
    return a+1

print (func())

This will print 6

But global variables should be avoided as much as possible

回答3:

Since a is define outside the function scope and before the functions are defined, you do not need to feed it as argument, you can simply use a. Python will first look whether the variable is defined in the function scope, if not, it looks outside that scope.

a = ['A','X','R','N','L']

def fun1(string):
    out = []
    for letter in a:
        out.append(string+letter)
    return out

def fun2(number):
    out = []
    for letter in a:
        out.append(str(number)+letter)
    return out

x = fun1('Hello ')
y = fun2(2)

In this case you can also rewrite your functions into more elegant list comprehensions:

a = ['A','X','R','N','L']

def fun1(string):
    return [string+letter for letter in a]

def fun2(number):
    return [str(number)+letter for letter in a]

x = fun1('Hello ')
y = fun2(2)

来源：https://stackoverflow.com/questions/41636867/how-to-share-variable-between-functions-in-python

标签

python

function

variables

input