Python小技巧

文章目录

1. 1. 交换变量
2. 2. 行内if语句
3. 3. 连接
4. 4. 数字技巧
5. 5. 数值比较
6. 6. 同时迭代两个列表
7. 7. 带索引的列表迭代
8. 8. 列表推导式
9. 9. 字典推导
10. 10. 初始化列表
11. 11. 列表转换成字符串

交换变量

x = 6
y = 5
x,y = y,x

行内if语句

print "Hello" if True else "World"	#  Hello

连接

不同类型的对象连接

nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
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

数字技巧

5.0//2 	#  向下取整 2
2**5 	#  2的5次方
.3/.1	#  2.9999999999999996
.3//.1	#  2.0

数值比较

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

同时迭代两个列表

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

带索引的列表迭代

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

列表推导式

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

字典推导

teams = ["Packers", "49ers", "Ravens", "Patriots"]
print {key: value for value, key in enumerate(teams)}

初始化列表

items = [0]*3

列表转换成字符串

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