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The following are some Python practical tips and tools that I have collected in recent years. I hope they can be helpful to you.
x = 6 y = 5 x, y = y, x print x >>> 5 print y >>> 6
print "Hello" if True else "World" >>> Hello
The last one below This method is very cool when binding two objects of different types.
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
#除后向下取整 print 5.0//2 >>> 2 # 2的5次方 print 2**5 >> 32
Pay attention to the division of floating point numbers
print .3/.1 >>> 2.9999999999999996 print .3//.1 >>> 2.0
This is one of the few languages I have seen that is so awesome Simple method
x = 2 if 3 > x > 1: print x >>> 2 if 1 0: print x >>> 2
Iterate two lists simultaneously
nfc = ["Packers", "49ers"] afc = ["Ravens", "Patriots"] for teama, teamb in zip(nfc, afc): print teama + " vs. " + teamb >>> Packers vs. Ravens >>> 49ers vs. Patriots
Indexed list iteration
teams = ["Packers", "49ers", "Ravens", "Patriots"] for index, team in enumerate(teams): print index, team >>> 0 Packers >>> 1 49ers >>> 2 Ravens >>> 3 Patriots
Given a list, we can The method of brushing to select an even number list:
numbers = [1,2,3,4,5,6] even = [] for number in numbers: if number%2 == 0: even.append(number)
changes to the following:
numbers = [1,2,3,4,5,6] even = [number for number in numbers if number%2 == 0]
Isn’t it awesome, haha.
Similar to list comprehension, a dictionary can do the same job:
teams = ["Packers", "49ers", "Ravens", "Patriots"] print {key: value for value, key in enumerate(teams)} >>> {'49ers': 1, 'Ravens': 2, 'Patriots': 3, 'Packers': 0}
Initialize the value of the list
items = [0]*3 print items >>> [0,0,0]
Convert the list to String
teams = ["Packers", "49ers", "Ravens", "Patriots"] print ", ".join(teams) >>> 'Packers, 49ers, Ravens, Patriots'
I admit that the try/except code is not elegant, but here is a simple method, try to find the key in the dictionary, if not found The corresponding alue will be set to its variable value using the second parameter.
data = {'user': 1, 'name': 'Max', 'three': 4} try: is_admin = data['admin'] except KeyError: is_admin = False
Replace with this:
data = {'user': 1, 'name': 'Max', 'three': 4} is_admin = data.get('admin', False)
Sometimes, you only need some of the elements in a list. Here are some ways to get a subset of a list.
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]
Some time ago Jeff Atwood promoted a simple programming exercise called FizzBuzz. The question is quoted as follows:
Write a The program prints the numbers 1 to 100, replacing the number with "Fizz" for multiples of 3, "Buzz" for multiples of 5, and "FizzBuzz" for numbers that are both multiples of 3 and 5. Here is a short, interesting way to solve this problem:for x in range(101): print"fizz"[x%3*4::]+"buzz"[x%5*4::] or xCollectionIn addition to python's built-in
from collections import Counter print Counter("hello") >>> Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1})Iteration toolLike the collections library, there is also a library called itertools, which can really solve certain problems efficiently. One of the use cases is to find all combinations, which can tell you all the impossible combinations of elements in a group
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 == TrueThis is a very interesting thing compared to practical technology. In python, True and False is a global variable, so:
False = True if False: print "Hello" else: print "World" >>> Hello
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