python笔记

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  一、数字

>>> 17 / 3  # classic division returns a float
5.666666666666667
>>>
>>> 17 // 3  #保留整数 floor division discards the fractional part
5
>>> 17 % 3  # 余数 the % operator returns the remainder of the division
2
>>> 5 * 3 + 2  # result * divisor + remainder
17

还可以使用**运算符计算幂乘方：

>>> 5 ** 2  # 5 squared
25
>>> 2 ** 7  # 2 to the power of 7
128

二、字符串

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:

>>> print(‘C:\some\name‘)  # here \n means newline!
C:\some
ame
>>> print(r‘C:\some\name‘)  # note the r before the quote
C:\some\name

字符串可以跨多行。一种方法是使用三引号："""..."""或者‘‘‘...‘‘‘。行尾换行符会被自动包含到字符串中，但是可以在行尾加上 \ (续行符)来避免这个行为。下面的示例：

print("""Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to
""")

将生成以下输出（注意，没有开始的第一行）：

Usage: thingy [OPTIONS]
     -h                        Display this usage message
     -H hostname               Hostname to connect to

>>> # 3 times ‘un‘, followed by ‘ium‘
>>> 3 * ‘un‘ + ‘ium‘
‘unununium‘


三、索引
第一个字符的索引值为0

>>> word = ‘Python‘
>>> word[0]  # character in position 0
‘P‘
>>> word[5]  # character in position 5
‘n‘

>>> word[-1]  # last character
‘n‘
>>> word[-2]  # second-last character
‘o‘
>>> word[-6]
‘P‘

>>> word[0:2]  # characters from position 0 (included) to 2 (excluded)
‘Py‘
>>> word[2:5]  # characters from position 2 (included) to 5 (excluded)
‘tho‘

>>> word[:2]  # character from the beginning to position 2 (excluded)
‘Py‘
>>> word[4:]  # characters from position 4 (included) to the end
‘on‘
>>> word[-2:] # characters from the second-last (included) to the end
‘on‘

 注、试图使用太大的索引会导致错误：

python笔记

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原文地址：http://www.cnblogs.com/yxtk/p/5691475.html