给Python初学者的一些编程技巧

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

if 语句在行内
 

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

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cool。

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 worldprint nfc, 1>>> ['Packers', '49ers'] 1

数字技巧
 

#除后向下取整print 5.0//2>>> 2# 2的5次方print 2**5>> 32

注意浮点数的除法
 

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

数值比较

这是我见过诸多语言中很少有的如此棒的简便法
 

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

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>>> Packers vs. Ravens>>> 49ers vs. Patriots

带索引的列表迭代
 

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

列表推导式

已知一个列表，我们可以刷选出偶数列表方法：
 

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

转变成如下：
 

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

是不是很牛呢，哈哈。

字典推导

和列表推导类似，字典可以做同样的工作：
 

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

初始化列表的值
 

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

列表转换为字符串
 

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

从字典中获取元素

我承认try/except代码并不雅致，不过这里有一种简单方法，尝试在字典中查找key，如果没有找到对应的alue将用第二个参数设为其变量值。