运算
数字运算
- 运算会根据结果自动判断结果是int还是float
- 用到除法的时候，结果自动输出为float
- 双斜杠
//得到的结果是int
- 取模(余数)还是
%
>>> 2+2
4
>>> 50-5*6
20
>>> (50-5*6)/4
5.0
>>> 8/5
1.6
>>> 5.0/1.6
3.125
>>> 17//3
5
>>> 17%3
2
- 赋值
=
- 多次方
2**7 2的7次方
- 完全支持浮点型和整型混合运算
- 最后一个值会被被赋给变量
_,
- 保留小数点,如保留2位
round(num,2)
# 赋值
>>> width = 20
>>> height = 30
>>> width * height
600
# 阶乘
>>> 2**7
128
>>> 5**2
25
# 默认赋值符
>>> 4*3.5+5-8.5
10.5
>>> _*3
31.5
>>> _+0.123
31.623
# 保留小数点
>>> round(_,2)
31.62
字符串
# 相同引号不转义会报错
>>> 'It's'
File "<stdin>", line 1
'It's'
^
SyntaxError: invalid syntax
# 转义
>>> 'It\'s'
"It's"
>>> "\"Yes,\" he said."
'"Yes," he said.'
# 不同引号可以直接包含
>>> "It's"
"It's"
# \n是换行符
>>> print('line\nnewline')
line
newline
# 加r 使用原始字符串
>>> print(r'line\nnewline')
line\nnewline
# 换行符
>>> print("""
... hello
... world
... """)
hello
world
# 换行，防止空行
>>> print("""\
... hello
... world
... """)
hello
world
# 字符串 + * 运算
>>> print(3*" hello " + 'world')
hello hello hello world
# 字符串自动拼接
>>> 'python' ' good'
'python good'
字符串索引
>>> content = 'hello world'
# 正索引
>>> content[0]
'h'
>>> content[5]
' '
>>> content[9]
'l'
# 后端索引
>>> content[-1]
'd'
>>> content[-5]
'w'
# 连续索引
# content[包括:不包括]
>>> content[:5] # 0-5
'hello'
>>> content[4:5] # 4-5
'o'
>>> content[0:] # 0-end
'hello world'
>>> content[-10:] # end-(end-10)
'ello world'
# 长度
>>> len(content)
11
Lists
# 列表不同的项之间用逗号隔开
# 最好后面再加个空格，和下面打印出来的一样
>>> list = [1,2,3,4,5,100]
>>> list
[1, 2, 3, 4, 5, 100]
# 索引，和字符串一样
>>> list[2]
3
>>> list[-2]
5
>>> list[-2:]
[5, 100]
>>> list[:-2]
[1, 2, 3, 4]
# 全部请求
>>> list[:]
[1, 2, 3, 4, 5, 100]
# 连接list
>>> list + [101,102]
[1, 2, 3, 4, 5, 100, 101, 102]
# 可变类型
>>> list[1] = 11
>>> list
[1, 11, 3, 4, 5, 100]
# 追加操作
>>> list.append(103)
>>> list
[1, 11, 3, 4, 5, 100, 103]
# 胡求变
>>> list
[1, 11, 3, 4, 5, 100, 103]
>>> list[1:3] = ['A','b','C']
>>> list
[1, 'A', 'b', 'C', 4, 5, 100, 103]
>>> list[0:2] = []
>>> list
['b', 'C', 4, 5, 100, 103]
>>> list = []
>>> list
[]
# 列表嵌套及运算
>>> a = [2,3,4]
>>> b = [3,4,5]
>>> list = [a,b]
>>> list
[[2, 3, 4], [3, 4, 5]]
>>> list = list + a + b
>>> list
[[2, 3, 4], [3, 4, 5], 2, 3, 4, 3, 4, 5]
>>> list[1]
[3, 4, 5]
>>> list[5]
3
>>> list[0][2]
4
# 斐波那契数列(注意...格式,否则会报错)
>>> a,b = 0,1
>>> while b< 1000:
... print(b,end=',')
... a,b = b,a+b
...
1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,>>>
