Function Parameters as References

"""
from Fluent Python 2nd Example 6-11
"""

def f(p1, p2):
    p1 += p2
    return p1

x, y = 1, 2
f(x, y)
# x = 1, y = 2

a = [1, 2]
b = [3, 4]
f(a, b)
# a 的值改变了
# a = [1, 2, 3, 4]
# b = [3, 4]

m = (1, 2)
n = (3, 4)
f(m, n)
# m = (1, 2)
# n = (3, 4)