# variables
lecture_day = 2
print(lecture_day)# numbers can be int, float or complex
square_area = 36
circle_area = 6.28
iota = (-1) ** (1/2)
print(square_area, circle_area, iota)# basic mathematical operators
print(square_area + circle_area)
print(4 * square_area)
print(iota/square_area)
# type function
print(type(iota))# strings
greeting = "Hello from Scaler!"
print(greeting)
# f-strings
msg = "Hello from"
name = "Scaler"
print(f"{msg} {name}!")# input from user
num1 = int(input())
num2 = int(input())
print(num1 + num2)# none value
x = None
print(x)- comparison operators (<, >, <=, >=)
- Equals (==)
- Not equals (!=)
- and
- or
- not
# comparison operators
a = 3
less_than_3 = a < 3
print(less_than_3) # False
print(type(less_than_3)) # <class 'bool'># other relational operators: >, >=, ==, !=
print(a == 3) # True
print(a != 3) # False# logical operators: or, and, not
x = 5
res_one = x < 1 or x > 10
res_two = x >= 1 and x <= 10
print(res_one) # False
print(res_two) # True
user_logged_in = True
print(not user_logged_in)# the integer 0 is always False, and every other number, is True
x = bool(0)
y = bool(-1)
z = bool(1)
print(x, y, z) # False True True# strings are compared lexicographically, i.e. by ASCII value of the characters
# you can remeber that capital letters come before lower case ones
print("Scaler" > "Interviewbit") # True as 'S' comes after 'I'
print('s' > 'S') # True
print("Scaler" == "Interviewbit") # False# Identity comparisons, is keyword is used
# if the compared objects are stored in the same memory location, returns true
a = "Scaler"
b = "Scaler"
print(a is b)
print(id(a))
print(id(b))# bitwise operators
a = 3
b = 5
c = a & b
'''
Bitwise AND (&)
In result, bit is set at those positions where it is set in both the operands
011
& 101
---
001
---
'''
print(c)# Exercise
a = False
b = True
c = True
print (a or b and c)
# Read about operator precedences-
Decision making statements in programming languages decide the direction of flow of program execution.
-
There comes situations in real life when we need to make some decisions and based on these decisions, we decide what should we do next.
-
Similar situations arise in programming also where we need to make some decisions and based on these decision we will execute the next block of code.
-
Majorly, the following 3 conditional constructs are used in Python:
- if
- else
- elif
'''
This program checks if a message is rude or polite
A message is rude if the parameter x is less than 1 or greater than 10
'''
x = int(input())
if (x < 1):
print("Rude message")
if (x > 10):
print("Rude message")'''
The problem with the above code is redundancy!
A principal rule of programming is to never ever have
two pieces of code to do the same thing.
It can be improved as shown below:
'''
if (x < 1 or x > 10):
print("Rude message")
if (x >= 1 and x <= 10):
print("Polite message")'''
The problem with above code is robustness
what if the condition of rudeness changes and we will have to
rewrite both the conditions above,
we can simplify it using an else construct :)
'''
if (x < 1 or x > 10):
print("Rude message")
else:
print("Polite message")# if elif
# say if only x < 1 are rude messages
# from 1 to 10 are polite messages
# and after 10 are other types!
if (x < 1):
print("Rude messsage")
elif (x >= 1 and x <= 10):
print("Polite message")
else:
print("Any other message")vegetable_market = ["onion", "tomato", "broccoli", "cabbage"]
if "carret" in vegetable_market:
print("Bought carret!")
elif "cabbage" in vegetable_market:
print("Bought cabbage!")
else:
print("Came back empty handed...")- Frequently we want a program to keep doing the same thing over and over again until something happens. That’s called looping.
- Let’s say you are playing a game in which you get a score of 2 points every 1 second as long as you are alive in the game. Is that an example of loop?
- Say you need to print numbers from 1 to 10 to the screen, how will you do it?
- We will see the following 2 types of loops:
- for: It is used when we know how many times our loop body will get executed or can decide it before the loop starts.
- while: It is used when the loop will break upon some condition returning false which we might not be sure when exactly that would happen.
- Nested loops (loop inside a loop) are also required at places, for e.g. consider a train it has multiple compartments, and each compartment has multiple seats, so the ticket checker loops over each compartment, and in each compartment, further loops over each of the seats!
range(n)includes all numbers from 0 to (n - 1)range(1, n)includes all numbers from 1 to (n - 1)range(1, n, 2)includes all numbers from 1 to (n - 1) with a step increment of 2- You can use
list(range(...))to show the numbers in the range used.
# print numbers from 1 to 10 to the screen
'''
print(1)
print(2)
...
print(10)
The above is not a good practice since our requirement
might change and we might have to print from 1 to n, where n is the input.
Also, the code is repititive, that is why language provides loop constructs!
'''
# for loops in python do not have initialization, condition, update statement like in other langs
# in keyword is used along with for, to iterate over items in a container or sequence
for n in range(10):
print(n, end=' ')
print() # by default, end = '\n'# the above code prints '0 1 2 ... 9'
# we want to print '1 2 3 ... 10'
for n in range(1, 11):
print(n, end=' ')
print()# let us say we want to print all even numbers from 1 to 10
for n in range(2, 11, 2):
print(n, end=' ')
print()# can use list operator before range, to print the items in the range
print(list(range(2, 11, 2)))# doing the same thing using a while loop
counter = 0
while (counter < 10):
counter += 1
print(counter, end=' ')
print()
# NOTE: while loops usually have a statement to update the sentinel value (being checked in condition)
# otherwise the loop can run infinitely, use Ctrl-C to exit the infinite loop
# the loop below runs infinitely
'''
counter = 0
while (counter < 10):
print(counter, end=' ')
''''''
Program to find sum of digits of a number
'''
n = int(input())
# say n = 1234, how do you compute the sum of the digits?
# you see all the digits, 1, 2, 3, 4, and add them up in a go, boom => 10 is the answer
# How do we program the computer to do this for us?
# We should follow the same technique, right?
# Loop through all the digits, and add them up one by one!
# So, our computer will store the result at some place, we need to create a variable
# Say sum = 0
# How to find a particular digit?
# n = 1234, can we say last digit is the one we get after finding remainder when n is divided by 10
# i.e. n % 10 = 4, add this 4 to the sum, now sum = 4
# Now, we can divide n by 10, to get n' = 1234//10 = 123 (integer division!)
# We continue this process, until n becomes zero!!!
# Pseudocode:
'''
n = input from user
sum = 0
while (n > 0)
d = last digit of n (i.e. n % 10)
add d to sum
divide n by 10
print(sum)
'''sum = 0
while (n > 0):
d = n % 10
sum += d # shorthand for sum = sum + d
n //= 10 # shorthand for n = n//10
print(sum)
# Try yourself:
# 1. Count digits in a number
# 2. Reverse a number
# 3. Find all factors of a number'''
Program to print multiplication tables of numbers from 1 to n
'''
n = int(input())
for multiple in range(1, 11):
for number in range(1, n + 1):
print(number*multiple, end=' ')
print()
# formatted output
for multiple in range(1, 11):
for number in range(1, n + 1):
print("%4d"%(number*multiple), end=' ')
print()- break
- continue
- Let’s take a real scenario where we can use break statements.
- Let us consider a repetitive task to send email to 100 employees.
- Suppose after sending 10 emails, suddenly internet disconnected. What action you will perform at that time?
- You can either attempt a try to send rest 90 emails, which will result in error. Alternatively, you can terminate the mailing process with a warning or error message.
- Definitely, it is better to postpone or terminate the mailing process for now than sending mails further that will result in error.
# break and continue allow to control the flow of the loops
# using break, we can go outside the loop
names = ["Scaler", "Interviewbit", "scaler", "interviewbit"]
for name in names:
print(name)
if (name == "Scaler"):
break# using continue, we can skip a particular iteration, and go to next one
for name in names:
if (name == "Scaler"):
continue
print(name)# using break in nested loops
# break in the inner loop just breaks out of the inner loop
# outer loop will continue to run
target = 'i'
for name in names:
print(f"{name} in outer loop")
for char in name:
if char == target:
print(f"Found {name} with letter: {target}")
print("Breaking out of the inner loop")
break# Exercise:
# Write a program to check if a given number is prime, use the break statement wisely!- Consider it to be a black box that takes serveral inputs, does some processing and can return some output
- To write a program, either we can have a single big piece of code file which will become difficult to maintain, so we use functions and break our code into small tasks, i.e. functions
- Reusability
- Abstraction
- To use a function, you only need to know its name and the arguments it accepts.
- You need not know how it works internallly.
- Modular design
- Maintenance
- Debugging
- It becomes a lot easier if we know the exact function where the code is breaking!
def print_function():
print("This function just prints to the screen!")
x = print_function() # Function which does not return anything, returns 'None'
print(x)
'''
Output:
This function just prints to the screen!
None
'''def sum_of_two(num_1, num_2):
return num_1 + num_2
res = sum_of_two(1, 100)
print(res)# functions can accept arguments with default values (called as keyword arguments)
def greetings(name="Scaler"):
print(f"Hello from {name}")
greetings()
greetings("InterviewBit")# Exercise, complete the following function that returns maximum of three numbers
# def max_of_three(num_1, num_2, num_3)