Python Notes

 Quick python revision notes

# formating

name = 'bhagvant'

f = f"this is {name}"

print(f)

# Notice we are not adding f

name = 'bhagvant'

greeting = 'hello {}'

k = greeting.format(name)

################ LIST ###########################

l = ["Bob", "Rolf", "Anne"]

l[0] = "Smith"

l.append("Jen")

# extend allows to add set or tuple to list, l+s will not work , works only for list

s = {"Bob", "Rolf", "Anne"}

l.extend(s)

print(l)

# we can even insert a set to list

l[0] = s

#gets the length of list

len(l)

# Get number of times element appears in list

print(l.count("Bob"))

# to remove element from given inde type POP

l.pop(2)

l.pop() # removes last element

# reverse a list

l.reverse()

# sorts a list

prime_numbers = [11, 3, 7, 5, 2]

prime_numbers.sort()

############ Tuple ##############################

# you can concat 2 tuples but cant , change element of tuple

tuple1 = (0, 1, 2, 3)

tuple2 = ('python', 'geek')

 

# Concatenating above two

print(tuple1 + tuple2)

################# SET ##########################

# sets are unordered, Cannot contain duplicates and efficient for searching elements

friends = {"Bob", "Rolf", "Anne"}

abroad = {"Bob", "Anne"}

# to Create a set you cant use {} , this will create empty dictionary

a = set()

s.add("Jen")

# set cant have same element twice , its distinct

s.add("Bob")

print(friends.difference(abroad))

# returns empty set

print(abroad.difference(friends))

print(friends.intersection(abroad))

friends = {"Bob", "Rolf", "Anne"}

abroad = {"Bob", "Anne"}

# superset

if friends > abroad :

    print('superset')

   

# subset

if abroad < friends:

    print('subset')

# easy to check key in , fastest data structure due to hash table

for name in friends:

    if name in abroad:

        print(f' {name} gone abroad')

############# Is operator #######################

if 2 variables point to same object

x = 5

y = 5

print(x is y)

############ If condition #####################

dayofweek = 'Monday'

if dayofweek == 'Monday':

    print(1)

######### in keyword #################

# The `in` keyword works in most sequences like lists, tuples, and sets.

friends = ["Rolf", "Bob", "Jen"]

print("Jen" in friends)

# --

movies_watched = {"The Matrix", "Green Book", "Her"}

user_movie = input("Enter something you've watched recently: ")

print(user_movie in movies_watched)

############ LOOPS #######################

while n < 5:

    print(n)

    n+=1

   

while True:

    break

   

for i in range(10):

    print(f'for {i}')

#How to have 2 loops and loop through

for i in range(_size):

    k = i + 1

    for j in range(k, _size):

# remember when range start and end are equal it will not print

for i in range(1,1):

    print('wont print')

# incrementing range by 2 every time

for i in range(0,6,2):

    print(i)

########### List comprehension ###################

print([i for i in range(10) if i in [2,4,6]])

######## Dicationaries ##################

friend_ages = {"Rolf": 24, "Adam": 30, "Anne": 27}

print(friend_ages.keys())

print(friend_ages.values())

print(friend_ages['bhagvant'])

# adding to dictionary

friend_ages['bhagvant'] = 54

   

# Simple

student_attendance = {"Rolf": 96, "Bob": 80, "Anne": 100}

for student in student_attendance:

    print(f"{student}: {student_attendance[student]}")

# better

for i,k in friend_ages.items():

    print(i,k)

############## Functions #####################

def abc(a=1,b=2):

    print('this is function',a,b)

   

abc(1,3)

def abc(a=1,b=2):

    print('this is function',a,b)

    c = a+b

    return c

   

total = abc(1,3)

########## Lambda ############################

#map allows to add lambda to sequence

l = [1,2,3,4,5]

sum1 = lambda x:x+1

map_object = map(sum1,l)

   

print(list(map_object))

# * packs arguments into sinle list

a,*b = 1,2,3,4

print('first',a,b)

# unpacks it into tuple

def abc(k,*a):

    print(a)

    print(k)

   

abc(1,2,3,4)

# it packs the values into dictionary

def abc(**kwargs):

    print(kwargs)

   

abc(a='kk',b='jj')

anotherfunctionwithKeyValue(**kwargs)

def abc(**kwargs):

    print(kwargs)

    # allows to pass it

    anotherfunctionwithKeyValue(**kwargs)

   

abc(a='kk',b='jj')

########## Object oriented programming ###################

class abc:

    # notice init has to have self as argument

    def __init__(self,a=0,b=0):

        self.c = a+b

        # all class variables need self

   

    # self has to be passed as argument

    def multi(self):

        print(self.c)

     

    # used to print info about class , shoudl have a return

    def __str__(self):

        return f"value of a is {self.c}"

       

   

k = abc(1,1)

k.multi()

# str gets called when you print class ref

print(k)