python之cookbook-day01

第一章：数据结构和算法

1.1 解压序列赋值给多个变量

>>> p = (4, 5)
>>> x, y = p
>>> x
4
>>> y
5
>>>
>>> data = [ 'acme', 50, 91.1, (2012, 12, 21) ]
>>> name, shares, price, date = data
>>> name
'acme'
>>> date
(2012, 12, 21)
>>> name, shares, price, (year, mon, day) = data
>>> name
'acme'
>>> year
2012
>>> mon
12
>>> day
21

#如果变量个数和序列元素个数不匹配，则会产生一个异常
>>> p = (4, 5)
>>> x, y, z = p
traceback (most recent call last):
file "<stdin>", line 1, in <module>
valueerror: need more than 2 values to unpack
>>>

>>> s = 'hello'
>>> a, b, c, d, e = s
>>> a
'h'
>>> b
'e'
>>> e
'o'

#如果只想解压一部分而舍弃其他值，可以使用占位符
>>> data = [ 'acme', 50, 91.1, (2012, 12, 21) ]
>>> _, shares, price, _ = data
>>> shares
50
>>> price
91.1