Python Parameter Passing Note

　　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。

0:

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

 

1:

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]

3:

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]

　　通过这样方法来理解参数传递，省去了我们的很多的考虑，个人感觉这种方法还是很不错的，不知道各位大神们是怎么理解Python中的参数传递的？