除法
>>> 8 / 5
1 >>> 8 / 5.0 1.6 >>> 8.0 / 5 1.6 >>> 8 // 5.0 1.0
余数
>>> 8 % 5
2
**运算符
>>> 5 ** 2
25
=运算符
>>> width = 20
>>> height = 5*9 >>> width * height 900
_变量,表示最近一次表达式的值
>>> _
900
字符串输出
>>> ‘spam eggs‘
‘spam eggs‘ >>> "span eggs"
‘spam eggs‘
>>> ‘"Yes," he said.‘
‘"Yes," he said.‘
转义
说明:输出的字符串会用引号引起来,特殊字符会用反斜杠转义。
虽然可能和输入看上去不太一样(外围的引号会改变),但是两个字符串是相等的。
如果你前面带有\的字符被当作特殊字符,你可以使用原始字符串,方法是在第一个引号前面加上一个r:
>>> ‘doesn\‘t‘
"doesn‘t" >>> "\"Yes,\" he said."
‘"Yes," he said.‘ >>> r‘doesn\‘t‘
"doesn\‘t" >>> 8 // 5.0 1.0
字符串跨多行(""")
>>> print """Usage: thingy [OPTIONS] -h
-H hostname """
Usage: thingy [OPTIONS] -h -H hostname
字符串连接
>>> ‘Py‘ + ‘thon‘
‘Python‘ >>> ‘Py‘ ‘thon‘
‘Python‘
>>> ‘Py‘ * 3
‘PyPyPy‘
字符串的索引
>>> word = ‘Python‘
>>> word[0]
‘P‘
>>> word[5]
‘n‘
索引为负数时,此时从右侧开始计数(因为-0和0是一样的,索引索引从-1开始)
>>> word = ‘Python‘
>>> word[-1]
‘n‘
>>> word[-6]
‘P‘
切片(截取字符串)
>>> word = ‘Python‘
>>> word[0:2]
‘Py‘
>>> word[2:5]
‘tho‘
包含起始的字符,不包含末尾的字符。这使得s[:i] + s[i:]永远等于s:
>>> word = ‘Python‘
>>> word[:2] + word[2:]
‘Python‘
切片的索引有非常有用的默认值;省略的第一个索引默认为零,省略的第二个索引默认为切片的字符串的大小
>>> word = ‘Python‘
>>> word[:2]
‘Py‘
>>> word[4:]
‘on‘
>>> word[-2:]
‘on‘
当用于切片时,超出范围的切片索引会被优雅地处理:
>>> word = ‘Python‘
>>> word[4:42]
‘on‘
>>> word[42:]
‘‘
内置函数len()
>>> word = ‘Python‘
>>> len(word)
6
Unicode字符串
创建Unicode字符串与创建普通字符串一样简单,u表示内置函数unicode()
>>> u‘Hello World !‘
u‘Hello World !‘
如果字符串中包含特殊字符,可以使用Unicode转义编码
>>> u‘Hello\u0020World !‘
u‘Hello World !‘
Unicode字符串的raw模式
>>> ur‘Hello\\u0020World !‘
u‘Hello\\\\u0020World !‘
列表
>>> squares = [1, 4, 9, 16, 25]
>>> squares
[1, 4, 9, 16, 25]
和字符串(以及其他所有内置的序列类型)一样,列表可以索引和切片
>>> squares = [1, 4, 9, 16, 25]
>>> squares[0]
1
>>> squares[-1]
25
>>> squares[-3:]
[9, 16, 25]
列表也支持连接
>>> squares = [1, 4, 9, 16, 25]
>>> squares + [36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
列表是可变的(字符串是不可变的)
>>> squares = [1, 4, 9, 16, 25]
>>> cubes[3] = 33
>>> cubes
[1, 4, 9, 33, 25]
append()方法
>>> cubes= [1, 4, 9]
>>> cubes.append(16)
>>> cubes
[1, 4, 9, 16]
给切片赋值,此操作甚至可以改变列表的大小或者清空它
>>> letters = [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘]
>>> letters[2:5] = [‘C‘, ‘D‘, ‘E‘]
>>> letters
[‘a‘, ‘b‘, ‘C‘, ‘D‘, ‘E‘, ‘f‘, ‘g‘]
>>> letters[2:5] = []
>>> letters
[‘a‘, ‘b‘, ‘f‘, ‘g‘]
>>> letters
[‘a‘, ‘b‘, ‘C‘, ‘D‘, ‘E‘, ‘f‘, ‘g‘]
len函数
>>> letters = [‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘]
>>> len(letters)
4
嵌套列表
>>> a = [‘a‘, ‘b‘, ‘c‘]
>>> n = [1, 2, 3]
>>> x = [a, n]
>>> x
[[‘a‘, ‘b‘, ‘c‘], [1, 2, 3]]
>>> x[0]
[‘a‘, ‘b‘, ‘c‘]
>>> x[0][1]
‘b‘
时间: 2024-10-13 10:58:59