運(yùn)算

數(shù)字運(yùn)算

運(yùn)算會(huì)根據(jù)結(jié)果自動(dòng)判斷結(jié)果是int還是float

用到除法的時(shí)候，結(jié)果自動(dòng)輸出為float

雙斜杠//得到的結(jié)果是int

取模(余數(shù))還是%

>>> 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

賦值 =

多次方 2**7 2的7次方

完全支持浮點(diǎn)型和整型混合運(yùn)算

最后一個(gè)值會(huì)被被賦給變量_,

保留小數(shù)點(diǎn),如保留2位round(num,2)

# 賦值

>>> width = 20

>>> height = 30

>>> width * height

600

# 階乘

>>> 2**7

128

>>> 5**2

25

# 默認(rèn)賦值符

>>> 4*3.5+5-8.5

10.5

>>> _*3

31.5

>>> _+0.123

31.623

# 保留小數(shù)點(diǎn)

>>> round(_,2)

31.62

字符串

# 相同引號(hào)不轉(zhuǎn)義會(huì)報(bào)錯(cuò)

>>> 'It's'

File "", line 1

'It's'

^

SyntaxError: invalid syntax

# 轉(zhuǎn)義

>>> 'It\'s'

"It's"

>>> "\"Yes,\" he said."

'"Yes," he said.'

# 不同引號(hào)可以直接包含

>>> "It's"

"It's"

# \n是換行符

>>> print('line\nnewline')

line

newline

# 加r 使用原始字符串

>>> print(r'line\nnewline')

line\nnewline

# 換行符

>>> print("""

... hello

... world

... """)

hello

world

# 換行，防止空行

>>> print("""\

... hello

... world

... """)

hello

world

# 字符串 + * 運(yùn)算

>>> print(3*" hello " + 'world')

hello hello hello world

# 字符串自動(dòng)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'

# 連續(xù)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'

# 長(zhǎng)度

>>> len(content)

11

Lists

# 列表不同的項(xiàng)之間用逗號(hào)隔開

# 最好后面再加個(gè)空格，和下面打印出來的一樣

>>> list = [1,2,3,4,5,100]

>>> list

[1, 2, 3, 4, 5, 100]

# 索引，和字符串一樣

>>> list[2]

3

>>> list[-2]

5

>>> list[-2:]

[5, 100]

>>> list[:-2]

[1, 2, 3, 4]

# 全部請(qǐng)求

>>> list[:]

[1, 2, 3, 4, 5, 100]

# 連接list

>>> list + [101,102]

[1, 2, 3, 4, 5, 100, 101, 102]

# 可變類型

>>> 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]

# 胡求變

>>> 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

[]

# 列表嵌套及運(yùn)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

# 斐波那契數(shù)列(注意...格式,否則會(huì)報(bào)錯(cuò))

>>> 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,>>>

總結(jié)

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