儿童学习python的一些小技巧

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

print "Hello" if True else "World"
> Hello

nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
print nfc + afc
> ['Packers', '49ers', 'Ravens', 'Patriots']
print str(1) + " world"
> 1 world
print `1` + " world"
> 1 world
print 1, "world"
> 1 world
print nfc, 1
> ['Packers', '49ers'] 1

print 5.0//2
> 2
# 2的5次方
print 2**5
 32

print .3/.1
> 2.9999999999999996
print .3//.1
> 2.0

x = 2
if 3 > x > 1:
print x
> 2
if 1 < x > 0:
print x
> 2

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 {key: value for value, key in enumerate(teams)}
> {'49ers': 1, 'Ravens': 2, 'Patriots': 3, 'Packers': 0}

items = [0]*3
print items
> [0,0,0]

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

data = {'user': 1, 'name': 'Max', 'three': 4}
try:
is_admin = data['admin']
except KeyError:
is_admin = False
data = {'user': 1, 'name': 'Max', 'three': 4}
is_admin = data.get('admin', False)

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')
False == True

False = True
if False:
print "Hello"
else:
print "World"
> Hello