the python function list (list) when "the pit" when the parameter "a pit

#!/usr/bin/env python3


def compute(base, value):
    base.append(value)
    result = sum(base)
    print(result)

if __name__ == '__main__':
    testlist = [10, 20, 30]
    compute(testlist, 15)
    compute(testlist, 25)
    compute(testlist, 35)

　　

In Python function, parameter passing, if there is a default for the list (list), then we should note, here there is a pit!

The expected output is:

Python3 /home/shiyanlou/listbugtest.py $
75
85
95
but now the program output is:

$ python3 /home/shiyanlou/listbugtest.py
75
100
135

 

 

Basic, please refer to: https://blog.csdn.net/ztf312/article/details/81010274

def f(x,li=[]):
    for i in range(x):
        li.append(i*i)
    print (li)
 
print('---1---')
f(4)
print('---2---')
f(5)

　　expected results:

---1---
[0, 1, 4, 9]
---2---
[0, 1, 4, 9, 16]

　　Results of the:

---1---
[0, 1, 4, 9]
---2---
[0, 1, 4, 9, 0, 1, 4, 9, 16]

　　optimization:

def f(x, li=[]):
    if not li:
        # If li is not empty, then you go down (empty list); do not go empty
        = []
    for i in range(x):
        li.append(i * i)
    print (li)


print('---1---')
f(4)
print('---2---')
f(5)
print('---3---')
f(6)