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字典的学习2——参考Python编程从入门到实践

程序员文章站 2022-04-08 12:53:06
遍历字典 1. 遍历所有键值对 eg1: for key, value in user_0.items(): 也可简化为 for k, v in user_0.items(): 但对于这两个变量是可以使用任何名称,并不局限于此。 eg2: 打印出每个人喜欢的语言 2.遍历字典中的所有键 找出两位朋友 ......

遍历字典

1. 遍历所有键值对

eg1: 

user_0 = {
'username': 'efermi',
'first': 'enrico',
'last': 'fermi',
}
for key, value in user_0.items():
print("\nkey: " + key)
print("value: " + value)

for key, value in user_0.items(): 也可简化为 for k, v in user_0.items(): 但对于这两个变量是可以使用任何名称,并不局限于此。

eg2: 打印出每个人喜欢的语言

favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
for name, language in favorite_languages.items():
print(name.title() + "'s favorite language is " + language.title() + ".")

2.遍历字典中的所有键

for name in favorite_languages.keys():
print(name.title())

或省略keys(),输出不变
for name in favorite_languages:
print(name.title())

找出两位朋友喜欢的语言:

friends = ['phil', 'sarah']
for name in favorite_languages.keys():
if name in friends:
print("hi " + name.title() + ", i see your favorite language is " + favorite_languages[name].title() + "!")

确定某个人是否接受了调查

if 'eric' not in favorite_languages.keys():
print("erin, please take our poll!")

3. 按顺序遍历字典中的所有键

for name in sorted(favorite_languages.keys()):
print(name.title() + ", thank you for taking the poll.")

调用sorted( )函数让字典中所有键在遍历前排序。

4. 遍历字典中的所有值

print('the following languages have been mentioned:')
for language in favorite_languages.values():
print(language.title())

运行结果:

the following languages have been mentioned:
python
c
ruby
python

打印出了字典中的所有值,但字典中的值是可以重复的,结果也就出现了重复,为此可以使用集合set( )提出重复:

print('the following languages have been mentioned:')
for language in set(favorite_languages.values()):
print(language.title())

运行结果:

the following languages have been mentioned:
python
ruby
c

note: 遍历字典时,键值的返回顺序是不定的,键和值的对应是固定。