17 tips for beginners of Python

17 practical tips for beginners of Python to swap variables

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

If statement in line

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

Connection

The last method below looks cool when binding two different types of objects.

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

Computing skills

# Round down print 5.0 // 2 >>> 2 # print 2 ** 5> 32

Pay attention to the division of floating point numbers.

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

Numerical comparison

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

Iteration of both lists

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

List iteration with index

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

List derivation

If a list is known, the method for selecting an even number list is as follows:

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

Replace the following

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

Dictionary derivation

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

Value of the initialization list

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

Converts a list to a string.

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

Retrieve element from dictionary

Do not use the following methods

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

Replace

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

Get sublist

X = [1, 2, 3, 4, 5, 6] # The first three print x [: 3] >>> [1, 2, 3] # four middle print x [] >>> [,] # The last three print x [-3:] >>>>, 6] # print x [: 2] >>> [1, 3, 5] # print x [1: 2] >>>> [2, 4, 6]

Fix FizzBuzz with 60 characters

Some time ago, Jeff Atwood promoted a simple programming exercise called FizzBuzz. The problem is referenced as follows:

Write a program, print the numbers 1 to, and print "Fizz" in multiples of 3 to replace this number, and print "Buzz" in multiples of 5 ", print "FizzBuzz" for numbers that are multiples of 3 and multiples of 5 ".

Here is a short way to solve this problem:

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

Set

Counter database used

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

Iteration tools

Like the collections Library, there is also a library called 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')False == True

In python, True and False are global variables, so:

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