Python初学者的17个技巧

来源：互联网发布：工作软件开发经历编辑：程序博客网时间：2024/04/29 13:32

交换变量

x = 6y = 5x, y = y, xprint 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酷。

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

计算技巧

#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

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

两个列表同时迭代

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

已知一个列表，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)

用下面的代替

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

字典推导

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]

将列表转换成字符串

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

从字典中获取元素

不要用下列的方式

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

替换为

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

获取子列表

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print x[-3:]>>> [4,5,6]#奇数项print x[::2]>>> [1,3,5]#偶数项print x[1::2]>>> [2,4,6]

60个字符解决FizzBuzz

前段时间Jeff Atwood 推广了一个简单的编程练习叫FizzBuzz，问题引用如下：

写一个程序，打印数字1到100，3的倍数打印“Fizz”来替换这个数，5的倍数打印“Buzz”，对于既是3的倍数又是5的倍数的数字打印“FizzBuzz”。

这里有一个简短的方法解决这个问题：

for x in range(101):print"fizz"[x%3*4::]+"buzz"[x%5*4::]or x

集合

用到Counter库

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

迭代工具

和collections库一样，还有一个库叫itertools

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

在python中，True和False是全局变量，因此：

False = Trueif False:   print "Hello"else:   print "World">>> Hello

作者： IT程序狮
链接：http://www.imooc.com/article/1207
来源：慕课网

0 0