Python tricks

List comprehension

 squares = [x**2 for x in range(10)]

Dict Comprehension

 result = {x: x**2 for x in range(10)}

REMOVING DUPLICATES FROM THE LIST

  fruits = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
  new = list(set(fruits))
  ['banana', 'apple', 'pear', 'orange'] 

unpack from list

 fruit, num, date = ['apple', 5,(2021, 11, 7)]

list slice, sequence[start:stop:step]

  x = [10, 5, 13, 4, 12, 43, 7, 8]
  result = x[1:6:2]
  result [5, 4, 43]

Compare two Unordered list

from collections import Counter
one = [33, 22, 11, 44, 55]
two = [22, 11, 44, 55, 33]
Counter(one) == Counter(two)
sorted(one) == sorted(two)

Reverse String and List

print('Anand Tripathi'[::-1])
# ihtapirT dnanA
print([1,2,3][::-1])
# [3, 2, 1]

Inputting Secret Information
taking a username and password as input from the user

 from getpass import getpass
 uname = input('Enter Username: ')
 pwd = getpass('Enter password: ')
 print('Logging In....')

Opening a website

 import webbrowser
 webbrowser.open("https://medium.com/pythonistas")

The Walrus(:=) Operator
Normal Way :

  xs = [1,2,3]
  n=len(xs)
  if n>2:
     print(n)

Using walrus operators:

 xs = [1,2,3]
 if (n:=len(xs)>2):
     print(n)

Declare and assign the value at the same time

Difference between two lists
use the set’s symmetric_difference operation of the set of differences.

 list1 = ['Scott', 'Eric', 'Kelly', 'Emma', 'Smith']
 list2 = ['Scott', 'Eric', 'Kelly']set1 = set(list1)
 set2 = set(list2)list3 = list(set1.symmetric_difference(set2))
 # {'Smith', 'Emma'}
 # Or
 set1-set2
 # {'Smith', 'Emma'}

Merge two dictionaries or two lists

 # two dicts
 name = dict(first_name='Tom', last_name='Anderson')
 details = dict(age=28, sex='Male')
 person = {**name, **details}

 # two list
 list1 = ['Scott', 'Eric', 'Kelly']
 list2= list1 = ['Emma', 'Smith']
 whole_lst= [*list1, *list2]

For-else operation

 # For example assume that I need to search through a list and process each item until a flag   item is found and 
 # then stop processing. If the flag item is missing then an exception needs to be raised.
for i in mylist:
   if i == theflag:
      break
   process(i)
else:
    raise ValueError("List argument missing terminal flag.")

Converting lists into a dictionary

 user = [“Peter”, “John”, “Sam”]
 age = [23,19,34]
 dictionary = dict(zip(user, age))
 print(dictionary)