文章

Python入门小记(2)：if语句、字典、while循环

发表于
作者 2 分钟阅读

经过前面的学习，发现Python和之前接触到的编程语言，还是有很多相同之处，之后的记录，会着重记录比较特别的部分

if语句

1.Python中，if语句的写法示例(注意冒号的位置)

1
2
3
4
5
6
7
8

messge = 'We can find '
namelist = ['Jack', 'Tony', 'Alice']
if 'jack' in namelist:
    print(messge + 'jack')
elif namelist and 'Tony' in namelist:
    print(messge + 'Tony')
else:
    print(messge + 'nobody')

字典

1.在Python中，字典用放在花括号{}中的一系列键值对表示

1
2
3
4
5
6
7
8
9

letterValue = {'A': 1, 'B': 2, 'C': 3}
print(letterValue['A'])  # 1
letterValue['D'] = 3  # 添加新的键值对
del letterValue['B']  # 删除指定的键值对
print('D' in letterValue.keys())  # 判断字典中是否有此键，这里为True
print(letterValue)  # {'A': 1, 'C': 3, 'D': 3}
print([value for key, value in letterValue.items()])  # [1, 3, 3]
print([key for key in sorted(letterValue.keys(), reverse=True)])  # 对Key值按照倒序排列之后输出['D', 'B', 'A']
print([value for value in set(letterValue.values())])  # 输出去重后的结果[1, 3]

while循环

1.Python中的while也可以用continue,break等语句

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23

listName = []
name = ''
while True:
    name = input('Please enter your name:')
    if name.strip() == '':
        continue
    elif name != 'Quit':
        listName.append(name)
    else:
        break

print(listName)

# 运行结果
# Please enter your name:aa
# Please enter your name:
# Please enter your name:bb
# Please enter your name:cc
# Please enter your name:dd
# Please enter your name:ee
# Please enter your name:ff
# Please enter your name:Quit
# ['aa', 'bb', 'cc', 'dd', 'ee', 'ff']
编程语言, Python
Python
本文由作者按照 CC BY 4.0 进行授权