17个Python小技巧分享

1.交换变量

代码如下:
x = 6
y = 5

x, y = y, x

print x
>>> 5
print y
>>> 6

2.if 语句在行内

代码如下:
print "Hello" if True else "World"
>>> Hello

3.连接

下面的最后一种方式在绑定两个不同类型的对象时显得很酷。

代码如下:
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

4.计算技巧

代码如下:
#向下取整
print 5.0//2
>>> 2
# 2的5次方
print 2**5
>> 32

注意浮点数的除法

代码如下:
print .3/.1
>>> 2.9999999999999996
print .3//.1
>>> 2.0

5.数值比较

代码如下:
x = 2
if 3 > x > 1:
   print x
>>> 2
if 1 < x > 0:
   print x
>>> 2

6.两个列表同时迭代

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

7.带索引的列表迭代

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

8.列表推导

已知一个列表，刷选出偶数列表方法：

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

用下面的代替

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

9.字典推导

代码如下:
teams = ["Packers", "49ers", "Ravens", "Patriots"]
print {key: value for value, key in enumerate(teams)}
>>> {'49ers': 1, 'Ravens': 2, 'Patriots': 3, 'Packers': 0}

10.初始化列表的值

代码如下:
items = [0]*3
print items
>>> [0,0,0]

11.将列表转换成字符串

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

12.从字典中获取元素

不要用下列的方式

data = {'user': 1, 'name': 'Max', 'three': 4}