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Useful Snippets

1. All Unique

This method check if there is any duplicate element 

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def all_unique(lst):
        return len(str) == len(set(lst))

x = [1,1,2,2,3,2,3,4,5,6]
y = [1,2,3,4,5]
all_unique(x) # False
all_unique(y) # True

2. Anagrams

Check if a string is an anagram

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from collections import Counter

def anagram(first, second):
    return Counter(first) == Counter(second)

anagram("abcd3","3acdb") #True

3. Memory

This is use to check the memory usage of an object

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import sys

variable = 30
print(sys.getsizeof(variable))# 24

4. Byte size

This Method return the length of a string in bytes

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def byte_size(string):
    return(len(String.encode('utf-8')))

byte_size('😀') # 4
byte_size('Hello World') # 11

5. Print a String N times

This will print a string N times

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n = 2;
s = 'programing'

print(s*n) # ProgrammingProgramming

6. Capitalize first letters

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s = "programming is awesome"

print(s.title()) # Programming Is Awesome

7. Chunk

This method chunk a list in a smaller list of specific size

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from math import ceil

def chunk(lst, size):
    return list(map(lambda x: lst[x * size:x * size + size],list(range(0, ceil(len(lst) / size)))))

chunk([1,2,3,4,5],2) # [[1,2],[3,4],5]

8. Compact

This method remove the "Falsy" values, in other words, False, 0, None,"".

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def compact(lst):
    return list(filter(bool,lst))

compact([0, 1, False, 2, '', 3, 'a', 's', 34]) # [ 1, 2, 3, 'a', 's', 34 ]

9. Count by

This use ZIP() method to transpose a 2D array

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array = [['a'.'b'],['c','d'],['e'.'f']]
transposed = zip(*array)
print(transposed) # [('a', 'c', 'e'), ('b', 'd', 'f')]

10. chained comparison

multiple comparison in a single line

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a = 3
print( 2 < a < 8) # True
print(1 == a < 2) # False

11. Comma-separated

This snippet use the method .join() turn a list of strings into a single string with each element from the list separated by commas.

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hobbies = ["basketball", "football", "swimming"]

print("My hobbies are: " + ", ".join(hobbies)) # My hobbies are: basketball, football, swimming

12. Count vowels

This method counts the number of vowels (‘a’, ‘e’, ‘i’, ‘o’, ‘u’) found in a string, using regular expressions.

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import re

def count_vowels(str):
    return len(len(re.findall(r'[aeiou]', str, re.IGNORECASE)))


count_vowels('foobar') # 3
count_vowels('gym') # 0

13. Decapitalize

This method can be used to turn the first letter of the given string into lowercase.

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def decapitalize(string):
    return str[:1].lower() + str[1:]


decapitalize('FooBar') # 'fooBar'
decapitalize('FooBar') # 'fooBar'

14. Flatten

The following methods flatten a potentially deep list using recursion.

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def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret

def deep_flatten(lst):
    result = []
    result.extend(
        spread(list(map(lambda x: deep_flatten(x) if type(x) == list else x, lst))))
    return result


deep_flatten([1, [2], [[3], 4], 5]) # [1,2,3,4,5]

15. Difference

This method finds the difference between two iterables and display just the different number in the first iterable

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def difference(a, b):
    set_a = set(a)
    set_b = set(b)
    comparison = set_a.difference(set_b)
    return list(comparison)


difference([1,2,3], [1,2,4]) # [3]

16. Difference by

The following method returns the difference between two lists after applying a given function to each element of both lists.

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def difference_by(a, b, fn):
    b = set(map(fn, b))
    return [item for item in a if fn(item) not in b]


from math import floor
difference_by([2.1, 1.2], [2.3, 3.4],floor) # [1.2]
difference_by([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], lambda v : v['x']) # [ { x: 2 } ]

17. Chained function call

You can call multiple functions inside a single line.

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def add(a, b):
    return a + b

def subtract(a, b):
    return a - b

a, b = 4, 5
print((subtract if a > b else add)(a, b)) # 9

18. Has duplicates

The following method checks whether a list has duplicate values by using the fact that set() contains only unique elements.

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def has_duplicates(lst):
    return len(lst) != len(set(lst))


x = [1,2,3,4,5,5]
y = [1,2,3,4,5]
has_duplicates(x) # True
has_duplicates(y) # False

19. Merge two dictionaries

The following method can be used to merge two dictionaries.

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def merge_dictionaries(a, b)
   return {**a, **b}


a = { 'x': 1, 'y': 2}
b = { 'y': 3, 'z': 4}
print(merge_dictionaries(a, b)) # {'y': 3, 'x': 1, 'z': 4}

20. Convert two lists into a dictionary

The following method can be used to convert two lists into a dictionary.

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def to_dictionary(keys, values):
    return dict(zip(keys, values))


keys = ["a", "b", "c"]
values = [2, 3, 4]
print(to_dictionary(keys, values)) # {'a': 2, 'c': 4, 'b': 3}

21. Use enumerate

This method gets a dictionary as an input and then returns only the keys that are in this dictionary.

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list = ["a", "b", "c", "d"]
for index, element in enumerate(list):
    print("Value", element, "Index ", index, )
# ('Value', 'a', 'Index ', 0)
# ('Value', 'b', 'Index ', 1)
#('Value', 'c', 'Index ', 2)
# ('Value', 'd', 'Index ', 3)

22. Time spent

This snippet can be used to calculate the time it takes to execute a particular code.

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import time

start_time = time.time()

a = 1
b = 2
c = a + b
print(c) #3

end_time = time.time()
total_time = end_time - start_time
print("Time: ", total_time)

# ('Time: ', 1.1205673217773438e-05)

23. Try else

You can have an else clause as part of a try/except block, which is executed if no exception is thrown.

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try:
    2*3
except TypeError:
    print("An exception was raised")
else:
    print("Thank God, no exceptions were raised.")

#Thank God, no exceptions were raised.

24. Most frequent

This method returns the most frequent element that appears in a list.

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def most_frequent(list):
    return max(set(list), key = list.count)


list = [1,2,1,2,3,2,1,4,2]
most_frequent(list)

25. Palindrome

This method checks whether a given string is a palindrome. It initially converts the string into lower case, then removes non-alphanumeric characters from it. In the end, it compares the new string with the reversed version.

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def palindrome(string):
    from re import sub
    s = sub('[\W_]', '', string.lower())
    return s == s[::-1]


palindrome('taco cat') # True

26. Calculator without if-else

The following snippet shows how you can write a simple calculator without the need to use if-else conditions.

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import operator
action = {
    "+": operator.add,
    "-": operator.sub,
    "/": operator.truediv,
    "*": operator.mul,
    "**": pow
}
print(action['-'](50, 25)) # 25

27. Shuffle

This algorithm randomizes the order of the elements in a list by implementing the Fisher-Yates algorithm to do the ordering in the new list.

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from copy import deepcopy
from random import randint

def shuffle(lst):
    temp_lst = deepcopy(lst)
    m = len(temp_lst)
    while (m):
        m -= 1
        i = randint(0, m)
        temp_lst[m], temp_lst[i] = temp_lst[i], temp_lst[m]
    return temp_lst


foo = [1,2,3]
shuffle(foo) # [2,3,1] , foo = [1,2,3]

28. Spread

This method flattens a list similarly like [].concat(…arr) in JavaScript.

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def spread(arg):
    ret = []
    for i in arg:
        if isinstance(i, list):
            ret.extend(i)
        else:
            ret.append(i)
    return ret


spread([1,2,3,[4,5,6],[7],8,9]) # [1,2,3,4,5,6,7,8,9]

29. Swap values

A really quick way for swapping two variables without having to use an additional one.

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def swap(a, b):
  return b, a

a, b = -1, 14
swap(a, b) # (14, -1)

30. Get default value for missing keys

This snippet shows how you can get a default value in case a key you are looking for is not included in the dictionary.

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d = {'a': 1, 'b': 2}

print(d.get('c', 3)) # 3