Python

collection of some useful shortcuts

3 min2816:23 pm

The following are just a collection of some useful shortcuts and tools I’ve found in Python over the years. Hopefully you find them helpful.

Swapping Variables

1
2
3
4
5
6
7
8

x = 6
y = 5
x, y = y, x






print x






>>> 5






print y






>>> 6










Inline if Statement








1
2







print "Hello" if True else "World"






>>> Hello










Concatenations


The last one is a pretty cool way to combine objects of two different types.








1
2
3
4







nfc = ["Packers", "49ers"]






afc = ["Ravens", "Patriots"]






print nfc + afc






>>> ['Packers', '49ers', 'Ravens', 'Patriots']










 








1
2







print str(1) + " world"






>>> 1 world










 








1
2







print `1` + " world"






>>> 1 world










 








1
2







print 1, "world"






>>> 1 world










 








1
2







print nfc, 1






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










Number Tricks








1
2
3







#Floor Division (rounds down)






print 5.0//2






>>> 2










 








1
2
3







#2 raised to the 5th power






print 2**5






>> 32










Be careful with division and floating point numbers.








1
2
3
4
5







print .3/.1






>>> 2.9999999999999996












print .3//.1






>>> 2.0










Numerical Comparison

This is a pretty cool shortcut that I haven’t seen in too many languages.








1
2
3
4
5
6
7
8
9







x = 2












if 3 > x > 1:






    print x






>>> 2












if 1 < x > 0:






    print x






>>> 2










Iterate Through Two Lists at the Same Time








1
2
3
4
5
6
7
8







nfc = ["Packers", "49ers"]






afc = ["Ravens", "Patriots"]












for teama, teamb in zip(nfc, afc):






    print teama + " vs. " + teamb












>>> Packers vs. Ravens






>>> 49ers vs. Patriots










Iterate Through List With an Index








1
2
3
4
5
6
7
8







teams = ["Packers", "49ers", "Ravens", "Patriots"]






for index, team in enumerate(teams):






    print index, team












>>> 0 Packers






>>> 1 49ers






>>> 2 Ravens






>>> 3 Patriots










List Comprehension


With a list comprehension we can turn this:








1
2
3
4
5







numbers = [1,2,3,4,5,6]






even = []






for number in numbers:






    if number%2 == 0:






        even.append(number)










Into this:








1
2







numbers = [1,2,3,4,5,6]






even = [number for number in numbers if number%2 == 0]










Pretty sweet huh?


Dictionary Comprehension


Similar to the list comprehension we can also do a dictionary comprehension like this:








1
2
3







teams = ["Packers", "49ers", "Ravens", "Patriots"]






print {key: value for value, key in enumerate(teams)}






>>> {'49ers': 1, 'Ravens': 2, 'Patriots': 3, 'Packers': 0}










Initialize List Values








1
2
3







items = [0]*3






print items






>>> [0,0,0]










Converting a List to a String








1
2
3







teams = ["Packers", "49ers", "Ravens", "Patriots"]






print ", ".join(teams)






>>> 'Packers, 49ers, Ravens, Patriots'










Get Item From Dictionary


I’ll admit that try/except code doesn’t look the prettiest. Here’s a simple way to fix that with dictionaries. This will try to find the key in the dictionary and if it can’t be found it will set the variable to the second parameter.

Instead of:








1
2
3
4
5







data = {'user': 1, 'name': 'Max', 'three': 4}






try:






    is_admin = data['admin']






except KeyError:






    is_admin = False










Do this:








1
2







data = {'user': 1, 'name': 'Max', 'three': 4}






is_admin = data.get('admin', False)










Taking a Subset of a List


Sometimes you only want to run code over a portion of a list. Here are a few ways you can get the subset of a list.








 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21







x = [1,2,3,4,5,6]












#First 3






print x[:3]






>>> [1,2,3]












#Middle 4






print x[1:5]






>>> [2,3,4,5]












#Last 3






print x[-3:]






>>> [4,5,6]












#Odd numbers






print x[::2]






>>> [1,3,5]












#Even numbers






print x[1::2]






>>> [2,4,6]










FizzBuzz in 60 Characters


Here’s a short, fun way to solve the problem.








1







for x in range(1,101):print"Fizz"[x%3*4:]+"Buzz"[x%5*4:]or x










Collections


In addition to python’s built in datatypes they also include a few extra for special use cases in the collections module.








1
2
3
4







from collections import Counter












print Counter("hello")






>>> Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1})










Itertools


Along with the collections library python also has a library calleditertoolswhich has really cool efficient solutions to problems.








 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12







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


This is more of a fun one than a useful technique. In python True and False are basically just global variables. Thus:








1
2
3
4
5
6
7







False = True






if False:






    print "Hello"






else:






    print "World"












>>> Hello










 


				
						
	


					
							
	

						
	

	

					
					
					
					
										
										
										
					


	
Related Articles

	










										
					



	
	
	
		

		
Leave a Reply 
Your email address will not be published. Required fields are marked *
 
 



 


 
 
 


	

	
This site uses Akismet to reduce spam. Learn how your comment data is processed.