20 Python Snippets You Should Learn Today
Python is a no-BS programming language. Readability and simplicity of design are two of the biggest reasons for its immense popularity.
As the Zen of Python says:
Beautiful is better than ugly.
Explicit is better than implicit.
This is why it is worthwhile to remember some common Python tricks to help improve your code design. These will save you the trouble of surfing Stack Overflow every time you need to do something.
The following tricks will prove handy in your day-to-day coding exercises.
1. Reversing a String
The following snippet reverses a string using the Python slicing operation.
reverse_slice.py
# Reversing a string using slicing
my_string = "ABCDE"
reversed_string = my_string[::-1]
print(reversed_string)
# Output
# EDCBA
You can read more about this here.
2. Using rhe Title Case (First Letter Caps)
The following snippet can be used to convert a string to title case. This is done using the title() method of the string class.
my_string = "my name is chaitanya baweja"
# using the title() function of string class
new_string = my_string.title()
print(new_string)
# Output
# My Name Is Chaitanya Baweja
3. Finding Unique Elements in a String
The following snippet can be used to find all the unique elements in a string. We use the property that all elements in a set are unique.
unique_string.py
my_string = "aavvccccddddeee"
# converting the string to a set
temp_set = set(my_string)
# stitching set into a string using join
new_string = ''.join(temp_set)
print(new_string)
4. Printing a String or a List n Times
You can use multiplication (*) with strings or lists. This allows us to multiply them as many times as we like.
print_string.py
n = 3 # number of repetitions
my_string = "abcd"
my_list = [1,2,3]
print(my_string*n)
# abcdabcdabcd
print(my_list*n)
# [1,2,3,1,2,3,1,2,3]
An interesting use case of this could be to define a list with a constant value — let’s say zero.
n = 4
my_list = [0]*n # n denotes the length of the required list
# [0, 0, 0, 0]
5. List Comprehension
List comprehension provides us with an elegant way of creating lists based on other lists.
The following snippet creates a new list by multiplying each element of the old list by two.
list_comprehension.py
# Multiplying each element in a list by 2
original_list = [1,2,3,4]
new_list = [2*x for x in original_list]
print(new_list)
# [2,4,6,8]
You can read more about it here.
6. Swap Values Between Two Variables
Python makes it quite simple to swap values between two variables without using another variable.
a = 1
b = 2
a, b = b, a
print(a) # 2
print(b) # 1
7. Split a String Into a List of Substrings
We can split a string into a list of substrings using the .split() method in the string class. You can also pass as an argument the separator on which you wish to split.
string_split.py
string_1 = "My name is Chaitanya Baweja"
string_2 = "sample/ string 2"
# default separator ' '
print(string_1.split())
# ['My', 'name', 'is', 'Chaitanya', 'Baweja']
# defining separator as '/'
print(string_2.split('/'))
# ['sample', ' string 2']
8. Combining a List of Strings Into a Single String
The join() method combines a list of strings passed as an argument into a single string. In our case, we separate them using the comma separator.
combine_strings.py
list_of_strings = ['My', 'name', 'is', 'Chaitanya', 'Baweja']
# Using join with the comma separator
print(','.join(list_of_strings))
# Output
# My,name,is,Chaitanya,Baweja
9. Check If a Given String Is a Palindrome or Not
We have already discussed how to reverse a string. So palindromes become a straightforward program in Python.
my_string = "abcba"
if my_string == my_string[::-1]:
print("palindrome")
else:
print("not palindrome")
# Output
# palindrome
10. Frequency of Elements in a List
There are multiple ways of doing this, but my favorite is using the Python Counter class.
Python counter keeps track of the frequency of each element in the container. Counter() returns a dictionary with elements as keys and frequency as values.
We also use the most_common() function to get the most_frequent element in the list.
# finding frequency of each element in a list
from collections import Counter
my_list = ['a','a','b','b','b','c','d','d','d','d','d']
count = Counter(my_list) # defining a counter object
print(count) # Of all elements
# Counter({'d': 5, 'b': 3, 'a': 2, 'c': 1})
print(count['b']) # of individual element
# 3
print(count.most_common(1)) # most frequent element
# [('d', 5)]
11. Find Whether Two Strings are Anagrams
An interesting application of the Counter class is to find anagrams.
An anagram is a word or phrase formed by rearranging the letters of a different word or phrase.
If the Counter objects of two strings are equal, then they are anagrams.
from collections import Counter
str_1, str_2, str_3 = "acbde", "abced", "abcda"
cnt_1, cnt_2, cnt_3 = Counter(str_1), Counter(str_2), Counter(str_3)
if cnt_1 == cnt_2:
print('1 and 2 anagram')
if cnt_1 == cnt_3:
print('1 and 3 anagram')
12. Using the try-except-else Block
Error handling in Python can be done easily using the try/except block. Adding an else statement to this block might be useful. It’s run when there is no exception raised in the try block.
If you need to run something irrespective of exception, use finally.
try_except.py
a, b = 1,0
try:
print(a/b)
# exception raised when b is 0
except ZeroDivisionError:
print("division by zero")
else:
print("no exceptions raised")
finally:
print("Run this always")
13. Using Enumerate to Get Index/Value Pairs
The following script uses enumerate to iterate through values in a list along with their indices.
my_list = ['a', 'b', 'c', 'd', 'e']
for index, value in enumerate(my_list):
print('{0}: {1}'.format(index, value))
# 0: a
# 1: b
# 2: c
# 3: d
# 4: e
14. Check the Memory Usage of an Object
The following script can be used to check the memory usage of an object. Read more about it here.
memory_usage.py
import sys
num = 21
print(sys.getsizeof(num))
# In Python 2, 24
# In Python 3, 28
15. Merging Two Dictionaries
While in Python 2, we used the update() method to merge two dictionaries; Python 3.5 made the process even simpler.
In the script given below, two dictionaries are merged. Values from the second dictionary are used in case of intersections.
merge_dict.py
dict_1 = {'apple': 9, 'banana': 6}
dict_2 = {'banana': 4, 'orange': 8}
combined_dict = {**dict_1, **dict_2}
print(combined_dict)
# Output
# {'apple': 9, 'banana': 4, 'orange': 8}
16. Time Taken to Execute a Piece of Code
The following snippet uses the time library to calculate the time taken to execute a piece of code.
import time
start_time = time.time()
# Code to check follows
a, b = 1,2
c = a+ b
# Code to check ends
end_time = time.time()
time_taken_in_micro = (end_time- start_time)*(10**6)
print(" Time taken in micro_seconds: {0} ms").format(time_taken_in_micro)
17. Flattening a List of Lists
Sometimes you’re not sure about the nesting depth of your list, and you simply want all the elements in a single flat list.
Here’s how you can get that:
from iteration_utilities import deepflatten
# if you only have one depth nested_list, use this
def flatten(l):
return [item for sublist in l for item in sublist]
l = [[1,2,3],[3]]
print(flatten(l))
# [1, 2, 3, 3]
# if you don't know how deep the list is nested
l = [[1,2,3],[4,[5],[6,7]],[8,[9,[10]]]]
print(list(deepflatten(l, depth=3)))
# [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
Numpy flatten is a better way to do this if you have a properly formatted array.
18. Sampling From a List
The following snippet generates n number of random samples from a given list using the random library.
import random
my_list = ['a', 'b', 'c', 'd', 'e']
num_samples = 2
samples = random.sample(my_list,num_samples)
print(samples)
# [ 'a', 'e'] this will have any 2 random values
I have been recommended the secrets library for generating random samples for cryptography purposes. The following snippet will work only on Python 3.
import secrets # imports secure module.
secure_random = secrets.SystemRandom() # creates a secure random object.
my_list = ['a','b','c','d','e']
num_samples = 2
samples = secure_random.sample(my_list, num_samples)
print(samples)
# [ 'e', 'd'] this will have any 2 random values
19. Digitize
The following snippet will convert an integer into a list of digits.
num = 123456
# using map
list_of_digits = list(map(int, str(num)))
print(list_of_digits)
# [1, 2, 3, 4, 5, 6]
# using list comprehension
list_of_digits = [int(x) for x in str(num)]
print(list_of_digits)
# [1, 2, 3, 4, 5, 6]
20. Check for Uniqueness
The following function will check if all elements in a list are unique or not.
def unique(l):
if len(l)==len(set(l)):
print("All elements are unique")
else:
print("List has duplicates")
unique([1,2,3,4])
# All elements are unique
unique([1,1,2,3])
# List has duplicates
Conclusion
These were some short snippets I find extremely useful in my everyday work. 30 seconds of python helped a lot while researching for this story.
Thank you for reading this story. Hope you enjoyed it.
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