Python初学者的捷径[译]
下面列出的都是这些年总结的Python的有用的知识点和一些工具。希望对你有所帮助！交换变量值
x = 6
y = 5
x, y = y, x
print x
>>> 5
print y
>>> 6
内联if语句
print "Hello" if True else "World"
>>> Hello
联接
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
数字运算
#Floor Division (rounds down)
print 5.0//2
>>> 2
#2 raised to the 5th power
print 2**5
>> 32
注意float数做整除运算后的出来的还是整数
print .3/.1
>>> 2.9999999999999996
print .3//.1
>>> 2.0
数字对比
x = 2
if 3 > x > 1:
print x
>>> 2
if 1 < x > 0:
print x
>>> 2
同时遍历两个数组
nfc = ["Packers", "49ers"]
afc = ["Ravens", "Patriots"]
for teama, teamb in zip(nfc, afc):
print teama + " vs. " + teamb
>>> Packers vs. Ravens
>>> 49ers vs. Patriots
延伸阅读zip方法，请点这里。
遍历List并获得index
teams = ["Packers", "49ers", "Ravens", "Patriots"]
for index, team in enumerate(teams):
print index, team
>>> 0 Packers
>>> 1 49ers
>>> 2 Ravens
>>> 3 Patriots
理解List
这个：
numbers =
even = []
for number in numbers:
if number%2 == 0:
even.append(number)
可以写成：
numbers =
even =
理解Dictionary
和List很相似，Dictionary的这个可以写成：
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List的值
items = *3
print items
>>>
List转换为String
teams = ["Packers", "49ers", "Ravens", "Patriots"]
print ", ".join(teams)
>>> 'Packers, 49ers, Ravens, Patriots'
从Dictionary中取得Item
一般来说是这样的，用一个try-except块包裹起来以防要取得的key值不存在：
data = {'user': 1, 'name': 'Max', 'three': 4}
try:
is_admin = data['admin']
except KeyError:
is_admin = False
但是你可以这样：
data = {'user': 1, 'name': 'Max', 'three': 4}
is_admin = data.get('admin', False)
取List得子集
很简单的取子集的方法：
x =
#First 3
print x[:3]
>>>
#Middle 4
print x
>>>
#Last 3
print x[-3:]
>>>
#Odd numbers
print x[::2]
>>>
#Even numbers
print x
>>>
60个字符搞定FizzBuzz问题
FizzBuzz问题：写一个程序打印1到100的数字。遇到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”代替这个数字
for x in range(1,101):print"Fizz"+"Buzz"or x
这里就是List的一个知识点了。如果方括号里，冒号左边的数字式大于字符串长度的，那么什么都不会输出！也就是在非3或者5的倍数的时候什么都不会输出。
集合
在collections模块下的Counter，有时候也是很有用的。
from collections import Counter
print Counter("hello")
>>> Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1})
Itertools
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
在python里，True和False只不过是全局变量，所以：
False = True
if False:
print "Hello"
else:
print "World"
>>> Hello
如果你发现什么有趣的东西欢迎在下面补齐！
from：http://www.maxburstein.com/blog/python-shortcuts-for-the-python-beginner/
页:
[1]