Python小技巧

x=6
y=5
x,y=y,x
print x,y
>>>5,6

 # 2的5次方
 print 2**5
 >>>32

 nfc = ["Packers", "49ers"]
 afc = ["Ravens", "Patriots"]
 for teama, teamb in zip(nfc, afc):
 print teama + " vs. " + teamb
 >>> Packers vs. Ravens
 >>> 49ers vs. Patriots

 teams = ["Packers", "49ers", "Ravens", "Patriots"]
 for index, team in enumerate(teams):
 print index, team
 >>> 0 Packers
 >>> 1 49ers
 >>> 2 Ravens
 >>> 3 Patriots

 numbers = [1,2,3,4,5,6]
 even = []
 for number in numbers:
   if number%2 == 0:
     even.append(number)

 numbers = [1,2,3,4,5,6]
 even = [number for number in numbers if number%2 == 0]  

 teams = ["Packers", "49ers", "Ravens", "Patriots"]
 print ", ".join(teams)
 >>> 'Packers, 49ers, Ravens, Patriots'

x = [1,2,3,4,5,6]
#前3个
print x[:3]
>>> [1,2,3]
#中间4个
print x[1:5]
>>> [2,3,4,5]
#最后3个(方法1)
print x[-3:]
>>> [4,5,6]
#最后3个(方法2)
print x[3:7]
>>> [4,5,6]
#奇数项
print x[::2]
>>> [1,3,5]
#偶数项
print x[1::2]
>>> [2,4,6]

from collections import Counter
print Counter("hello")
>>> Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1})

from itertools import combinations
teams = ["Packers", "49ers", "Ravens", "Patriots"]
for game in combinations(teams, 2):
print game
>>> ('Packers', '49ers')
>>> ('Packers', 'Ravens')
>>> ('Packers', 'Patriots')
>>> ('49ers', 'Ravens')
>>> ('49ers', 'Patriots')
>>> ('Ravens', 'Patriots')

>>> a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> a[-4:-2]
[7, 8]