Cheetsheet

>>> print(type(10 + 5.7))
<class 'float'>

# Arithmetic
10 + 3  # 13
10 - 3  # 7
10 * 3  # 30
10 ** 3 # 1000
10 / 3  # 3.3333333333333335
10 // 3 # 3 --> floor division - no decimals and returns an int
10 % 3  # 1 --> modulo operator - return the reminder. Good for deciding if number is even or odd

# Converting Strings to Numbers
age = input("How old are you?")
age = int(age)
pi = input("What is the value of pi?")
pi = float(pi)

# Basic Functions
pow(5, 2)      # 25 --> like doing 5**2
abs(-50)       # 50
round(5.46)    # 5
round(5.468, 2)# 5.47 --> round to nth digit
bin(512)       # '0b1000000000' -->  binary format
hex(512)       # '0x200' --> hexadecimal format

first_name = "Shubham"
last_name = "Lad"
print(first_name + ' ' + last_name)

print("Shubham" + 5) # This line will give error

# We can use Type Conversion though

print("Shubham" + str(5))

age = 26

print("Hi " + first_name + ' ' + last_name ", You are " + str(age) + " years old")

# Formatted String - write f
print(f'hi {first_name} {last_name}, You are {age} years old')

# [start:stop:stepover]
>>> ek_string = "0123456789"
>>> ek_string[5]
'5'
>>> ek_string[0:]
'0123456789'
>>> ek_string[:7]
'0123456'
>>> ek_string[4:7]
'456'
>>> ek_string[0:7]
'0123456'
>>> ek_string[0::2]
'02468'
>>> ek_string[-1]
'9'
>>> ek_string[::-1]
'9876543210'

# Basic Methods
'  I am alone '.strip()               # 'I am alone' --> Strips all whitespace characters from both ends.
'On an island'.strip('d')             # 'On an islan' --> # Strips all passed characters from both ends.
'but life is good!'.split()           # ['but', 'life', 'is', 'good!']
'Help me'.replace('me', 'you')        # 'Help you' --> Replaces first with second param
'Need to make fire'.startswith('Need')# True
'and cook rice'.endswith('rice')      # True
'bye bye'.index('e')                  # 2
'still there?'.upper()                # STILL THERE?
'HELLO?!'.lower()                     # hello?!
'ok, I am done.'.capitalize()         # 'Ok, I am done.'
'oh hi there'.find('i')               # 4 --> returns the starting index position of the first occurrence
'oh hi there'.count('e')              # 2

my_age = input("Enter your name")

#Palindrome check
word = 'reviver'
p = bool(word.find(word[::-1]) + 1)
print(p) # True

>>> list1 = [1,2,3,4,5]
>>> list2 = ['a', 'b', 'c', 'd', 'e']
>>> list3 = [1, 2, 'a', True]

>>> list3[2] # access element
'a'

>>> ek_string[-1]
'9'

>>> list1[0::2]
[1,3,5]

>>> matrix = [
>>>     [1, 2, 3],
>>>     [4, 5, 6],
>>>     [7, 8, 9]
>>> ]
>>>
>>> matrix[1][0]
4

# Matrix
matrix = [[1,2,3], [4,5,6], [7,8,9]]
matrix[2][0] # 7 --> Grab first first of the third item in the matrix object

# Looping through a matrix by rows:
mx = [[1,2,3],[4,5,6]]
for row in range(len(mx)):
    for col in range(len(mx[0])):
        print(mx[row][col]) # 1 2 3 4 5 6

# Transform into a list:
[mx[row][col] for row in range(len(mx)) for col in range(len(mx[0]))] # [1,2,3,4,5,6]

# Combine columns with zip and *:
[x for x in zip(*mx)] # [(1, 3), (2, 4)]

>>> len(list1)
5

# Add to List
>>> list1.append(100) #changes list inplace
[1, 2, 3, 4, 5, 100]
>>> list1.insert(2, 200) #insert at index
[1, 2, 200, 3, 4, 5, 100]
>>> list1.extend([101, 102])
[1, 2, 200, 3, 4, 5, 100, 101, 102]

# Copy a List
>>> list4 = ['apples', 'pears', 'oranges']
>>> new_list = list4.copy()
>>> new_list2 = list4[:]

# Remove from List
>>> list1.pop() #removes the last element
>>> list1.pop(0) #remove the element at index
>>> list1.remove(4) #removes the first matching element
>>> list1.clear() #removes all the element from list

# Ordering
>>> list1.sort() #sort the list inplace in accending order
>>> list1.sort(reverse=True) #sort the list inplace in accending order
>>> sorted(list1) #sort and retun new list
>>> list1.reverse() #reverse the list
>>> list(reversed([1,2,5,3]))# [3, 5, 2, 1] --> reversed() returns an iterator

>>> list1.index(2) #give the index of the matching element
>>> list2.index('d', 0, 3) # (element, startIndex, endIndex)
>>> 'x' in basket #check if list contain the value

# Useful operations
>>> 1 in [1,2,5,3]  # True
>>> min([1,2,3,4,5])# 1
>>> max([1,2,3,4,5])# 5
>>> sum([1,2,3,4,5])# 15

# Get First and Last element of a list
>>> mList = [63, 21, 30, 14, 35, 26, 77, 18, 49, 10]
>>> first, *x, last = mList
>>> print(first) #63
>>> print(last) #10

>>> list(range(1, 100)) # will produce list of numbers from 1 to 99
>>> join_by = " "
>>> join_by.join(['Hi', 'my', 'name', 'is', 'Shubham']) 
'Hi my name is Shubham' # join method joins elements of list with join_by
>>> 

a, b, c, *other = [1,2,3,4,5,6,7,8,9]

# Advanced Functions
list_of_chars = list('Helloooo')                                   # ['H', 'e', 'l', 'l', 'o', 'o', 'o', 'o']
sum_of_elements = sum([1,2,3,4,5])                                 # 15
element_sum = [sum(pair) for pair in zip([1,2,3],[4,5,6])]         # [5, 7, 9]
sorted_by_second = sorted(['hi','you','man'], key=lambda el: el[1])# ['man', 'hi', 'you']
sorted_by_key = sorted([
                       {'name': 'Bina', 'age': 30},
                       {'name':'Andy', 'age': 18},
                       {'name': 'Zoey', 'age': 55}],
                       key=lambda el: (el['name']))# [{'name': 'Andy', 'age': 18}, {'name': 'Bina', 'age': 30}, {'name': 'Zoey', 'age': 55}]

>>> user = {
    'name': 'Shubham',
    'age': 26,
    'is_cool': True,
    'basket': [1,2,3]
}

>>> dict(name='Shubham') # return new directory

>>> user.get('age', 55) # get method retrives value of key, second param(optional) is default value if key not present.
>>> basket in user #return boolean if key present
>>> user.keys() # return list of keys
>>> user.values() #return list of values
>>> user.items() #return tuple with pair of key and value
>>> user.clear()
>>> user.copy()
>>> user.pop('age') #removed perticular field
>>> user.update({'age': 27}) #upsert the key into dict
>>> user['favourite_snack'] = 'Grapes'

#Remove key
>>> del user['name']
>>> user.pop('name', None)

>>> new_dict = dict([['name','Andrei'],['age',32],['magic_power',False]])  # Creates a dict from collection of key-value pairs.
>>> new_dict = dict(zip(['name','age','magic_power'],['Andrei',32, False]))# Creates a dict from two collections.


>>> {**my_dict, **{'cool': True} }                                         # {'name': 'Andrei Neagoie', 'age': 30, 'magic_power': False, 'favourite_snack': 'Grapes', 'cool': True}
>>> new_dict = dict([['name','Andrei'],['age',32],['magic_power',False]])  # Creates a dict from collection of key-value pairs.
>>> new_dict = dict(zip(['name','age','magic_power'],['Andrei',32, False]))# Creates a dict from two collections.

from collections import OrderedDict
# Store each person's languages, keeping # track of who responded first. 
programmers = OrderedDict()
programmers['Tim'] = ['python', 'javascript']
programmers['Sarah'] = ['C++']
programmers['Bia'] = ['Ruby', 'Python', 'Go']

for name, langs in programmers.items():
    print(name + '-->')
    for lang in langs:
      print('\t' + lang)

>>> my_tuple = (1,2,3,4,5)
>>> my_tuple[1] # return 2
>>> 
>>> my_tuple = ('apple','grapes','mango', 'grapes')
>>> apple, grapes, mango, grapes = my_tuple.   # Tuple unpacking
>>> len(my_tuple)                              # 4
>>> my_tuple[2]                                # mango
>>> my_tuple[-1]                               # 'grapes'

# Methods
>>> my_tuple.index('grapes') # 1
>>> my_tuple.count('grapes') # 2

# Zip
>>> list(zip([1,2,3], [4,5,6])) # [(1, 4), (2, 5), (3, 6)]

# unzip
>>> z = [(1, 2), (3, 4), (5, 6), (7, 8)] # Some output of zip() function
>>> unzip = lambda z: list(zip(*z))
>>> unzip(z)

>>> my_set = {1,2,3,4,5,5}
>>> my_set.add(100) #add value to set
>>> my_set.add(2) # 2 is already present in the set
>>> my_set.copy()
>>> my_set.clear() # {}
>>> my_set.remove(100)      # {1} --> Raises KeyError if element not found
>>> my_set.discard(100)     # {1} --> Doesn't raise an error if element not found

>>> my_list = [1,2,3,4,5,5]
>>> set(my_list)
{1, 2, 3, 4, 5
>>> list(my_set)
[1, 2, 3, 4, 5]
>>> 1 in my_set
>>> len(my_set)

>>> my_set = {1,2,3,4,5}
>>> your_set = {4,5,6,7,8,9,10}
>>> my_set.difference(your_set)
{1, 2, 3}
>>> my_set.discard(5) #inplace
{1, 2, 3, 4}
>>> my_set.difference_update(your_set) #it removes all common values
{1, 2, 3}
>>> my_set.union(your_set) #join sets together 
{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
>>> my_set | your_set #union
>>> my_set.intersection(your_set) #return common value
{4, 5}
>>> my_set & your_set #intersection
>>> my_set.isdisjoint(your_set) #return boolen true if nothing common or false
>>> my_set.issubset(your_set) #return boolean - if my_set present in your_set
>>> my_set.issuperset(your_set) #return boolen - if my_set contains your_set

age = 26

if age > 18 and age <= 50 and not(age == 27):
    print("Your are adult")
elif age > 50:
    print("Buddha ho gaya re tu")
elif not age:
    print("Paida to ho ja")
else:
    print("Baccha he tu")

# Ternery Operator
# condition_if_true if condition else condition_if_else

is_friend = True
can_message = "Message Allowed" if is_friend else "Not Allowed to Message"

>>> a = [1, 2, 3]
>>> b = a
>>> b is a 
True
>>> b == a
True

# Make a new copy of list `a` via the slice operator, 
# and assign it to variable `b`
>>> b = a[:] 
>>> b is a
False
>>> b == a
True

any([False, True, False])# True if at least one item in collection is truthy, False if empty.
all([True,1,3,True])     # True if all items in collection are true

for item in (1,2,3,4,5):
    for x in ['a', 'b', 'c']:
        print(str(item) + x)

>>> user = {
>>>     "name": "Shubham",
>>>     "age": 26,
>>>     "is_cool": True
>>> }
>>>
>>> for item in user:
>>>     print(item)
name
age
is_cool

>>> for item in user.items():
>>>     key, value = item
>>>     print(key, value)
>>>
>>> for key, value in user.items():
>>>     print(key, value)
>>>     
>>> for item in user.keys():
>>>     print(item)
>>>     
>>> for item in user.values():
>>>     print(item)

for number in range(0, 100): # 0 to 99
    print(number)

for _ in range(0, 10, 2): # (start, end, stepover)
    print(_)

for i, char in enumerate('Helllloooo'): # it gives index and value both
    print(i, char)

for i, number in enumerate(list(range(100))):
    print(i, number)
    if number == 50:
        print(f'index of 50 is: {i}')

from collections import Counter
colors = ['red', 'blue', 'yellow', 'blue', 'red', 'blue']
counter = Counter(colors)# Counter({'blue': 3, 'red': 2, 'yellow': 1})
counter.most_common()[0] # ('blue', 3)

i = 0

while i < 50:
    print(i)
    break
else: #else will only run if the loop completes without break statement
    print("done with all the work")

my_list = [1,2,3]

for item in my_list:
    print(item)

i = 0
while i < len(my_list):
    print(my_list[i])
    i += 1

while True:
    response = input('Say something')
    if (response == 'bye'):
        break

for letter in 'Python':     # This skips printing letter 'h'
   if letter == 'h':
      continue
   print('Current Letter :', letter)

for i in 'Python': # Empty loop
    # No error will be raised
    pass

def fun():
    pass

some_list = ['a', 'b', 'c', 'b', 'd', 'm', 'n', 'n']

duplicates = []
for value in some_list:
    if some_list.count(value) > 1:
        if value not in duplicates:
            duplicates.append(value)

print(duplicates)

def say_something():
    print("Hello Shubham")

say_something()

#parameters
def say_hello(name, emoji):
    print(f'Hello {name} {emoji}')

#arguments
say_hello("Shubham", "🤩")

#positional arguments
say_hello("Snehal", "😁")

#keyword arguments
say_hello(emoji='😎', name='Emily')

#default parameters
def say_hello(name='Alex', emoji='👨‍💻'):
    print(f'Hello {name} {emoji}')

say_hello('Shubham') #it will use default parameter for emoji

def sum(num1, num2):
    return num1 + num2

sum(5, sum(2, 8)) # retrun 15

# return another function
def sum(num1, num2):
    def another_func(n1, n2):
        return n1 + n2
    return another_func(num1, num2)

def get_multiplier(a):
    def out(b):
        return a * b
    return out

>>> multiply_by_3 = get_multiplier(3)
>>> multiply_by_3(10)
30

def sum(num1, num2):
    '''
    Info: This function return sum of two numbers passed
    '''
    return num1 + num2

print(sum.__doc__)

>>> help(sum)
Help on function sum in module __main__:

sum(num1, num2)
    Info: This function return sum of two numbers passed

>>> def super_func(*args, **kwargs):
>>>     print(args)
>>>     print(kwargs)
>>> # arguments should be grouped and subsequent
>>> super_func(1,2,3,4,5, num1=5, num2=10) # kewaord arguments automatically gets assigned to the **kwargs and everything else gets assigned to *args
(1, 2, 3, 4, 5) # args as tuples
{'num1': 5, 'num2': 10} # kwargs as dictionary
>>> head, *body, tail = [1,2,3,4,5]

def add(*a):
    return sum(a)

add(1, 2, 3) # 6

def highest_even(li):
    evens = []
    for item in li:
        if item % 2 == 0:
            evens.append(item)
    return max(evens)

print(highest_even([10,2,3,4,8,11]))

def multiply_by_2(li):
    new_list = []
    for item in li:
        new_list.append(item*2)
    return new_list

multiply_by_2()

if True:
    x = 10 # Global scope - X can be accessed outeside of the if condition

def some_func():
    total = 100 # Local scope - total can be accessed only inside this function

a = 1 # global scope

def parent():
    a = 10 # local scope - it creates new varibale in local scope
    def confusion():
        return a
    return confusion()

print(parent()) # print 10
print(a) # print 1

total = 0

def count():
    golbal total # if global not written here python will create local var
    total += 1
    return total

count()

def outer():
    x = 'local'
    def inner(): 
        nonlocal x # use parent variable
        x = 'nonlocal'
        print('inner: ', x)
    inner()
    print('outer: ', x)

outer()
# inner: nonlocal
# outer: nonlocal

my_list = [1,2,3]

def multiply_by_2(item):
    return item * 2 # right only action that you want to perform on each item

list(map(multiply_by_2, my_list)) # map(action, iterables)
# [2,4,6]

my_list = [1,2,3]

def only_odd(item):
    return item % 2 != 0

list(filter(only_odd, my_list))
# [1,3]

my_list = [1,2,3]
your_list = [10,20,30]

list(zip(my_list, your_list))
# [(1, 10), (2, 20), (3, 30)]

from functools import reduce

my_list = [1,2,3]

def accumulator(acc, item):
    return acc + item

reduce(accumulator, my_list, 0)
# 6

my_list = [char for char in 'hello']
my_list1 = [char for char in range(0,100)]
my_list2 = [num**2 for num in range(0, 100)]
my_list3 = [num**2 for num in range(0, 100) if num % 2 == 0]

my_set = {char for char in 'hello'}
my_set1 = {char for char in range(0, 100)}
my_set2 = {num**2 for num in range(0, 100)}
my_set3 = {num**2 for num in range(0, 100) if num % 2 == 0]}

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

my_dict = {key:val**2 for key, val in simple_dict.items()}
my_dict = {k:v**2 for k, v in simple_dict.items() if v%2 == 0}

some_list = ['a', 'b', 'c', 'b', 'd', 'm', 'n', 'n']

duplicates = list(set([x for x in some_list if simple_list.count(x) > 1]))

# main.py

import utility

utility.multiply(2,5)

# utility.py

def multiply(num1, num2):
    return num1 * num2

def devide(num1, num2):
    return num1 / num2

import folder.utility

folder.utility.something()

if __name__ == '__main__': # Runs main() if file wasn't imported.
    main()

import folder.other_folder.product

folder.other_folder.product.get_items()

from folder.other_folder import product

product.get_items()

from folder.other_folder.product import get_items, buy

get_items()
buy('apple')

from utility import *

import <module_name>
from <module_name> import <function_name>
import <module_name> as m
from <module_name> import <function_name> as m_function
from <module_name> import *

def count(start, step):
    while True:
        yield start
        start += step

>>> counter = count(10, 2)
>>> next(counter), next(counter), next(counter)
(10, 12, 14)

@decorator_name
def function_that_gets_passed_to_decorator():
    ...

from functools import wraps

def debug(func):
    @wraps(func)
    def out(*args, **kwargs):
        print(func.__name__)
        return func(*args, **kwargs)
    return out

@debug
def add(x, y):
    return x + y

class <name>:
    age = 80 # Class Object Attribute
    def __init__(self, a):
        self.a = a # Object Attribute

    @classmethod
    def get_class_name(cls):
        return cls.__name__

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age  = age

class Employee(Person):
    def __init__(self, name, age, staff_num):
        super().__init__(name, age)
        self.staff_num = staff_num

class A: pass
class B: pass
class C(A, B): pass

>>> C.mro()
[<class 'C'>, <class 'A'>, <class 'B'>, <class 'object'>]

try:
  5/0
except ZeroDivisionError:
  print("No division by zero!")

while True:
  try:
    x = int(input('Enter your age: '))
  except ValueError:
    print('Oops!  That was no valid number.  Try again...')
  else: # code that depends on the try block running successfully should be placed in the else block.
    print('Carry on!')
    break

raise ValueError('some error message')

try:
  raise KeyboardInterrupt
except:
  print('oops')
finally:
  print('All done!')

import sys
script_name = sys.argv[0]
arguments   = sys.argv[1:]

<file> = open('<path>', mode='r', encoding=None)

<file>.seek(0)                      # Moves to the start of the file.
<str/bytes> = <file>.readline()     # Returns a line.
<list>      = <file>.readlines()    # Returns a list of lines.
<file>.write(<str/bytes>)           # Writes a string or bytes object.
<file>.writelines(<list>)           # Writes a list of strings or bytes objects.

def read_file(filename):
    with open(filename, encoding='utf-8') as file:
        return file.readlines() # or read()

for line in read_file(filename):
  print(line)

def write_to_file(filename, text):
    with open(filename, 'w', encoding='utf-8') as file:
        file.write(text)

def append_to_file(filename, text):
    with open(filename, 'a', encoding='utf-8') as file:
        file.write(text)

import csv

# Read Rows from CSV File
def read_csv_file(filename):
    with open(filename, encoding='utf-8') as file:
        return csv.reader(file, delimiter=';')

# Write Rows to CSV File
def write_to_csv_file(filename, rows):
    with open(filename, 'w', encoding='utf-8') as file:
        writer = csv.writer(file, delimiter=';')
        writer.writerows(rows)

import json
<str>    = json.dumps(<object>, ensure_ascii=True, indent=None)
<object> = json.loads(<str>)

# Read Object from JSON File
def read_json_file(filename):
    with open(filename, encoding='utf-8') as file:
        return json.load(file)

# Write Object to JSON File
def write_to_json_file(filename, an_object):
    with open(filename, 'w', encoding='utf-8') as file:
        json.dump(an_object, file, ensure_ascii=False, indent=2)

import pickle
<bytes>  = pickle.dumps(<object>)
<object> = pickle.loads(<bytes>)

# Read Object from File
def read_pickle_file(filename):
    with open(filename, 'rb') as file:
        return pickle.load(file)

# Write Object to File
def write_to_pickle_file(filename, an_object):
    with open(filename, 'wb') as file:
        pickle.dump(an_object, file)

from time import time
start_time = time()  # Seconds since
...
duration = time() - start_time

from math import e, pi
from math import cos, acos, sin, asin, tan, atan, degrees, radians
from math import log, log10, log2
from math import inf, nan, isinf, isnan

from statistics import mean, median, variance, pvariance, pstdev

from random import random, randint, choice, shuffle
random() # random float between 0 and 1
randint(0, 100) # random integer between 0 and 100
random_el = choice([1,2,3,4]) # select a random element from list
shuffle([1,2,3,4]) # shuffles a list

import re
<str>   = re.sub(<regex>, new, text, count=0)  # Substitutes all occurrences.
<list>  = re.findall(<regex>, text)            # Returns all occurrences.
<list>  = re.split(<regex>, text, maxsplit=0)  # Use brackets in regex to keep the matches.
<Match> = re.search(<regex>, text)             # Searches for first occurrence of pattern.
<Match> = re.match(<regex>, text)              # Searches only at the beginning of the text.

from datetime import date, time, datetime, timedelta
from dateutil.tz import UTC, tzlocal, gettz

<D>  = date(year, month, day)
<T>  = time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, fold=0)
<DT> = datetime(year, month, day, hour=0, minute=0, second=0, ...)
<TD> = timedelta(days=0, seconds=0, microseconds=0, milliseconds=0,
                 minutes=0, hours=0, weeks=0)

<D/DTn>  = D/DT.today()         # Current local date or naive datetime.
<DTn>    = DT.utcnow()          # Naive datetime from current UTC time.
<DTa>    = DT.now(<tz>)         # Aware datetime from current tz time.