vineetkhemnani / python-tutorial

Operators in python

• +,-,*,/
• / => division in float
• // => division in floor (returns floor of division)
• ** => power
• 2 ** 3 => returns 8
• round((expression),place) for ex:-

print(round((8/3),1))
# rounds off ABOVE code to 1 decimal place
print(round((8/3),2))
# rounds off ABOVE code to 2 decimal place

• Another way to round off two decimal

formatted_num="{:.2f}".format(num)

Shorthands

• result=result/2 can be written as result/=2
• also result=result+2 can be written as result+=2 and so on

Template literals or f-strings(formatted strings)

score=0
height=1.2
isWinning=True
print(f"score is {score}, height is {height}, isWinning is {isWinning}")

Conditionals in python

Syntax

if height>120:
	print("yay you can sit in the rollercoaster")
else:
    print("Sorry! you cant ride in the rollercoaster")
	print("Wear taller pair of shoes")

Nested if-else and elif

print("Welcome to the rollercoaster!")
height = int(input("What is your height in cm? "))

if height>120:
	print("Yay!!! you can sit in the rollercoaster")
	age=int(input("Enter age: "))
	if age<12:
		print("Ticket price is $5")
	elif age>12 and age<=18:
		print("Ticket price is $7")
else:
	print("Sorry! you cant ride in the rollercoaster")
	print("Wear taller pair of shoes")

Indentation in if-else

print("Welcome to the rollercoaster!")
height = int(input("What is your height in cm? "))
bill=0


if height>120:
	print("Yay!!! you can ride in the rollercoaster")
	age=int(input("Enter age: "))
	if age<12:
		bill=5
		print("Child ticket is $5")
	elif age>12 and age<=18:
		bill=7
		print("Youth ticket is $7")
	else:
		bill=12
		print("Adult ticket is $12")
	
	wants_photo=input("do you want photos? type Y or N")
	if wants_photo=="Y":
		bill+=3
		print(f"Your bill is ${bill}")
else:
	print("Sorry! you cant ride in the rollercoaster")
	print("Wear taller pair of shoes")

Inbuilt functions

• lower() => changes the entire string to lowercase
• count("") => counts the number of times a character specified in brackets occurs
• count() is case sensitive

Randomizing numbers

• import random
• random.randint(a,b) - gives a random integer between a and b (a and b inclusive)
• random.random() - random float between 0 and 1 (1 excluded)

Modules in python (ex. random)

• Long piece of code divided into smaller chunks where each chunk is responsible for a different bit of functionality of program. These chunks are called MODULES

Creating modules

• main.py is the entry point of our code
• create a new file with .py extension and import it in main file
• use modulename.variable_name to access variable

Lists in python

states_of_america = ["Delaware", "Pennsylvania", "New Jersey", "Georgia", "Conneticuit", "Maryland", "South Carolina", "New Hampshire" "Virginia", "North Carolina"]
# order is very important as order is index
print(states_of_america[0])
# prints Delaware

• A positive index means from the starting index of the list for ex. print(states_of_america[2])=> prints 2nd from the starting of the list
• A negative index means from the ending of the list print(states_of_america[-2]) => prints 2nd from the ending of the list

print(states_of_america[2]) #prints Delaware
print(states_of_america[-2]) #prints Virginia

Changing data of list

• states_of_america[1] = "Pencilvania" Above code changes the 1st index from "Pennsylvania" to Pencilvania

Appending data to the list

• states_of_america.append("Hawaii") - adds "Hawaii" to the end of the list

Extending the list (append an array)

• states_of_america.extend(["South Dakota, New York"]) - adds a list to the end of the states_of_america

str.split("reg_exp")

• splits a string into a list based on the reg_exp for ex:-

intro = "Hello,My,Name,is,Vineet"
intro_list=intro.split(",")
print(intro_list)

Above output is ['Hello', 'My', 'Name', 'is', 'Vineet']

Nested lists

• fruits = ["strawberries", "Nectarines", "Apples", "Grapes", "Peaches", "Cherries", "Pears"]

• vegetables = ["Spinach", "Kale", "Tomatoes", "Celery", "Potatoes"]

• dirty_dozen=[fruits,vegetables] => 2 lists inside a list o/p- [['strawberries', 'Nectarines', 'Apples', 'Grapes', 'Peaches', 'Cherries', 'Pears'], ['Spinach', 'Kale', 'Tomatoes', 'Celery', 'Potatoes']]

Loops in Python

for loop

fruits=[
	"apple",
	"banana",
	"cherry",]
for fruit in fruits:
	print(fruit)
	print(fruit+" "+"pie")
	print(fruits) #prints thrice coz indentation means inside loop
print(fruits) #prints once coz outside loop

for loop within range

for number in range(a,b): print(number)

for number in range(1,10):
	print(number)

• Above code prints number from 1 to 9 (Excluding 10)

• If you want to specify the step-size or increment size, you need to specify a 3rd parameter in range

for number in range(0,10,3):
	print(number)

• Here "3" specifies the step size as in increment each time by 3
• So the loop runs for 1,4,7 i.e. three times

Some more random functions

• random.choice(list) - chooses a random element from the list
• random.shuffle(list) - shuffles the contents of the list in random order