字典setdefault方法的学习

dict.setdefault(key, default=None)

dict = {‘runoob‘: ‘菜鸟教程‘, ‘google‘: ‘Google 搜索‘}
 
print "Value : %s" %  dict.setdefault(‘runoob‘, None)
print "Value : %s" %  dict.setdefault(‘Taobao‘, ‘淘宝‘)

#!./usr/bin/env python
# -*- coding: utf-8 -*-
# Date: 2019/2/28

iterable = {‘user‘: ‘alex‘, ‘user1‘: ‘wusir‘, ‘user2‘: ‘xdc‘}
values = {‘user‘: [‘sch‘]}
other_value = ‘test‘

# demo1
for element in iterable:
    if element not in values:
        values[element] = []
    values[element].append(other_value)

print(iterable)　　# {‘user2‘: ‘xdc‘, ‘user‘: ‘alex‘, ‘user1‘: ‘wusir‘}
print(values)　　　# {‘user2‘: [‘test‘], ‘user‘: [‘sch‘, ‘test‘], ‘user1‘: [‘test‘]}


# demo2
for element in iterable:
    values.setdefault(element, []).append(other_value)

print(iterable)　　# {‘user2‘: ‘xdc‘, ‘user‘: ‘alex‘, ‘user1‘: ‘wusir‘}
print(values)　　　# {‘user2‘: [‘test‘, ‘test‘], ‘user‘: [‘sch‘, ‘test‘, ‘test‘], ‘user1‘: [‘test‘, ‘test‘]}