Python Parameter Passing Note

最新推荐文章于 2025-09-12 15:58:40 发布

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最新推荐文章于 2025-09-12 15:58:40 发布

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文章标签： python

原文链接：http://www.cnblogs.com/lxw0109/p/python_parameter_passing.html

本文提供4个Python Demo帮助初学者理解参数传递，包括传值、传引用、改变列表元素和修改元组元素。通过实例解析，深入浅出地解释了Python中的参数传递机制，对比了传值与传引用的区别，并给出了一种简化理解方法。

　　我刚刚开始学习Python, Python中的参数传递总是让我很困惑。我写了4个简单的Demo，帮助我理解Python的参数传递，希望对大家都能有所帮助。

def change(x):
    x = 1

a = 10
print('a is {0}'.format(a))
change(a)
print('a is {0}'.format(a))

Output:
a is 10
a is 10

def change1(x):
    x = [1, 2]
    
a = [10, 20]
print('a is {0}'.format(a))
change1(a)
print('a is {0}'.format(a))

Output:
a is [10, 20]
a is [10, 20]

2: ［NOTE］We should pay more attention to this demo.

def change2(x):
    x[:] = [1, 2, 4]

a = [10, 20]
print('a is {0}'.format(a))
change2(a)
print('a is {0}'.format(a))

Output:
a is [10, 20]
a is [1, 2, 4]

def change3(x):
    x[0] = [1, 2, 4]

a = [10, 20]
print('a is {0}'.format(a))
change3(a)
print('a is {0}'.format(a))

Output:
a is [10 20]
a is [[1, 2, 4], 20]]

　　对于参数传递，我总是用传值或者传址来理解，但在《Python基础教程》中建议我们用这样的方法来理解Python中的参数传递：（以Demo1为例说明）

1.#demo1 again:
2.def change1(x):
3.    x = [1, 2]
4.   
5.a = [10, 20]
6.print('a is {0}'.format(a))
7.change1(a)
8.print('a is {0}'.format(a))

#We can think it in the following way:
#5行：
a = [10, 20]
#7行：NOTE，用下面代码来理解参数传递
x = a
#3行：
x = [1, 2]