Refresher: Operators and Control Statements¶

Question¶

What is the output of the following? print(type("1"))

Choices

int
float
str
bool

Question¶

What is the output of the following? print(bool("0"))

Choices

True
False
Error

Explanation

print(bool("0"))

Rules for converting string to bool are: - Empty string will be converted to False. - Everything else will be converted to True.

Here we have a string "0", so it has some value, it is not empty, so it will be True.

Question¶

print("Rahul", "Rohit", "Emma Watson", sep = " ")
print("Yash KGF")

Choices

Rahul Rohit Emma Watson Yash KGF
Rahul Rohit Emma Watson Yash KGF
Not Sure

Explanation

print("Rahul", "Rohit", "Emma Watson", sep = " ")
print("Yash KGF")

We have specified sep as " ", and by default end will be a new line, so Yash KGF will be printed in a new line.

Question¶

What is the output of the following?

b = input() # input value = 234
print(type(b))

Choices

int
string
not sure

Operators¶

Before operators, we just understand what is expression, Expression: is just a simple equation we write.

Example of expression: a = b + c

Here, - a, b and c are variables, or we can also call these operands. - = and + are operators.

So, if we want to do certain operations then we need operators.

Operators are classified into different types based on their functionalities: 1. Arithmetic Operators. 2. Comparison Operators. 3. Assignment Operators. 4. Logical Operators.

Arithmetic Operators¶

Arithmetic Operators are used for arithmetic calculations. Different arithmetic operators are explained below:

Addition¶

+ is used for addition, it can not work at one value, it always takes two values.

Example:

a = 1
b = 4
print(a + b)

Output:

Type change in addition: - int + int -> int We can add an integer and integer value to get an int value. - float + float -> float, we can add float and float value to get float value. * int + float -> float, we can add integer and float value to get float value * int/float + bool -> int/float, we can add int/float and bool value and it will give int/float value as a result.

Example:

print(2.5 + True)

Output:

3.5

Here True will be converted to float value i.e. 1.0, and then it will be added to 2.5 which will give 3.5 as a result.

Example:

print(2.5 + False)

Output:

2.5

Here False will be converted to float value i.e. 0.0, and it will be added to 2.5 which will give 2.5 as a result.

string + string -> string (concatenation)

Example:

print('1' + '1')

Output:

Not allowed in Python: * int/float/bool + string, Python does not allow to add int/float/bool to string, it will give an error.

Example:

print('1' + 1)

Output:

TypeError Traceback (most recent call last)
Cell In[20], line 1
----> 1 print('1' + 1)
TypeError: can only concatenate str (not "int") to str

int/float/bool/string + None, we can not do any arithmetic operations wth none.

Example:

print(1 + None)

Output:

TypeError Traceback (most recent call last)
Cell In[24], line 1
----> 1 print(1 + None)
TypeError: unsupported operand type(s) for +: 'int' and 'NoneType'

Subtraction¶

- is used for Subtraction.

It can be directly used with constants. Example:

print(2 - 3)

Output:

-1

We can also perform subtraction on variables.

Example:

a = 1
a_b = 2
print(a - a_b)

Output:

-1

Type change in subtraction * int - int -> int * float - float -> float * int - float -> float * int/float - bool -> int/float

Example:

print(2.5 - True)

Output:

1.5

True will be converted into 1.0, and then it will subtracted.

Example:

print(2.5 - False)

Output:

2.5

False will be converted into 0.0, then it will subtracted.

Not allowed * string - string, in string subtraction is not allowed, we can add strings. * int/float/bool - string * int/float/bool/string - None

Multiplication¶

* is used for Multiplication.

Example:

print(2 * 3)

Output:

Type change in multiplication * int * int -> int * float * float -> float * int * float -> float * int/float * bool -> int/float, if multiplied by False, then we will always get 0 or 0.0, or if multiplied with True, then it will be the same number. * int * string -> string (duplication), we can multiply an integer with a string, it will duplicate the string to the number of times of integer value.

Example:

print('I am Sorry \n' * 10)

Output:

I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry
I am Sorry

Not allowed * string * string * float * string * int/float/bool/string * None

Division¶

/ is used for Division.

Example:

print(3 / 2)

Output:

1.5

Type change in division

int / int -> float Example:
```
print(2 / 2)
```

Output: ```plaintext= 1.0

* **float / float -> float**
* **int / float -> float**

**Not allowed**

* **string/string**
* **float/string**
* **int/float/bool/string / None**

**Example:**
```python
print(-3 / 2)

Output:

-1.5

Modulus (mod) - Remainder¶

% is a Modulus (mod) operator symbol, it calculates the remainder.

Example:

print(5 % 2)

Output:

Example:

print(8 % 3)

Output:

Type change in modulus - int % int -> int

Floor Division¶

// is the floor division operator, it first divides the number, and it gives the previous smaller integer value of the quotient as a result.

Example:

print(8 // 3)

Output:

floor: floor(-2.5) = -3 as a previous smaller integer of -2.5 is -3,

floor(3.25) = 3 as a previous smaller integer of 3.25 is 3.

Example:

import math
print(math.floor(-2.5))
print(int(-2.5))
print(math.floor(3.00001))

Output:

-3
-2
3

Type change in floor division - int/float // int/float -> integral part, floor division gives integer for float values division also, it always give integral floor value of float quotient.

Integer typecasting simply removes the number available after the decimal point, but floor division gives the previous smaller integer value of the quotient.

Power¶

** works as a power operator in Python.

Example:

print(2 ** 3)

Output:

It can have float values also.

Example:

print(2 ** 0.5)

Output:

1.4142135623730951

The above code gives us a square root of 2.

Type change in floor division - int/float ** int/float -> int/float

Example:

print(3.5 ** 2)

Output:

12.25

Question¶

What is the output of the following?

print(10 % 3)

Choices

0
1
2
3

Question¶

What is the output of the following?

print(2 ** 3)

Choices

5
6
7
8

Question¶

What is floor(2.0)? Choices

2
1
3

Question¶

print(-8 // 3)

Choices

-2.666
-2
-3

Explanation

print(-8 // 3)

As -8/3 = -2.6666666666666665, if we calculate its floor then it will be -3, as the previous integer value of -2.6666666666666665 is -3.

Comparison Operator¶

Comparison Operator is used for comparison, when we want to compare the value of two things, we can compare in the following ways. * Equal * Not Equal * Less than / Greater than * Less than and equal / Greater than and equal

Comparison Operator always returns bool, it always tells us True or False.

Equal¶

== is equal operator in Python.

Example:

print(2 == 2)

Output:

True

Example:

print(2 == 3)

Output:

False

We can compare: - int and int - int and float

Example:

print(2 == 2.0)

Output:

True

Example:

print(2 == 2.00001)

Output:

False

int and string

Example:

print(2 == '2')

Output:

False

int and None, if we compare a value with none, we always get a False result.

Example:

print(2 == None)

Output:

False

But we can compare any type value with any other value type.

Not Equal¶

!= is a not equal operator in Python.

Example:

print(2 != '2')

Output:

True

Example:

print('2' != '22')

Output:

True

Example:

print('Aakar' != 'Aakar')

Output:

False

Example:

print('ABC' != 'abc')

Output:

True

Explaination: As python is a case sensitive language so ABC and abc are considered different.

Less Than / Greater Than¶

Example:

print(2 < 3)

Output:

True

We can not compare integer and string values.

Example:

print(2 < '2')

Output:

TypeError Traceback (most recent call last)
Cell In[65], line 1
----> 1 print(2<'2')
TypeError: '<' not supported between instances of 'int' and 'str'

We can have a comparison between integer and float values.

Example:

print(2 < 2.0001)

Output:

True

We can not compare integer and None values.

Example:

print(2 < None)

Output:

TypeError Traceback (most recent call last)
Cell In[67], line 1
----> 1 print(2< None)
TypeError: '<' not supported between instances of 'int' and 'NoneType'

We can have a comparison between string and string values.

Example:

print('a' < 'b')

Output:

True

Example:

print('Vicky' < 'Kusum')  # Will be covered in String class

Output:

False

We can also do a comparison with negative values.

Example:

print(2 > -3.43)

Output:

True

Example:

print(100 >= 32)

Output:

True

Example:

print(31 <= -43)

Output:

False

Assignment Operator¶

= is an assignment operator, it will assigne value to the variable.

Example:

a = 2 + 5
print(a)

Output:

Shorthand¶

In place of a = a (op) b, we can write a (op)= b.

Example:

a = 1
a = a + 5
print(a)

a = 1
a += 5
print(a)

Output:

6
6

Example:

a = 11
a = a % 5
print(a)

a = 11
a %= 5
print(a)

Output:

1
1

Logical Operator¶

We have the following logical operators: * And (Both the values should be True then True otherwise False) * Or (Any of the values should be true then True otherwise False) * Not (Reverse)

Logical operator always takes bool as input

AND¶

The truth table of AND:

True and True -> True
True and False -> False
False and True -> False
False and False -> False

AND will only give True output, if we have both values True, otherwise in all other cases(if any one value is False) it will give us False.

Example:

(2 < 3) and (2 < 4)

Output:

True

Both conditions result is True, so AND will also give True.

Example:

('Aakar' == 'Aakar') and (-2 < -3)

Output:

False

(-2<-3) gives False, so AND will also give False.

OR¶

The truth table of OR:

True or True -> True
True or False -> True
False or True -> True
False or False -> False

OR will give a True output, if any one of the input values is True, and it will give False only if both input values are False.

Example:

(2 < 3) or (2 < 4)

Output:

True

Example:

('Aakar' == 'aakar') or (-2 < -3)

Output:

False

Both conditions give us False, so the output will also be False.

Example:

('Aakar' == 'aakar')

Output:

False

Example:

(-2 < -3)

Output:

False

Not¶

not is Not operator. Truth Table * not True -> False * not False -> True

Example:

not ('Aakar' == 'aakar')

Output:

True

('Aakar' == 'aakar') will give us False, and not False gives us True.

Question¶

What is the output of the following? print(10 <= 8)

Choices

True
False

Question¶

What is the output of the following? print(False == 1)

Choices

True
False
Error

Question¶

What is the output of the following? print('1' < 2)

Choices

True
False
Error

Question¶

What is the output of the following?

a = 3
a *= 4
print(a)

Choices

3
4
7
12

Question¶

What is the output of the following?

print(True and (not False))

Choices

True
False
Error

Conditional Statements¶

A conditional statement is a Boolean expression that, if True, executes a piece of code. A conditional statement has some conditions, if it will be true then we have some piece of code to execute, and if it is false, then we have another piece of code to execute.

There are the following Conditional patterns in Python:

if
if else
if elif
if elif else

Python is an indentation-based language, in place of curly braces for blocks we use the same indentation for a single block code.

if¶

if(<condition>):
    this
    is
    a
    block

() is not necessary in Python for specifying the conditions.

Any number of spaces can give us an indentation, but a single block has the same indentation for all lines.

Example:

if(2 < 3):
    print('two is less')

Output:

two is less

If we add extra indentation in the same block, then it will give an error.

Example:

if(2 < 3):
    print('two is less')
        print('yayy') # will not work because of extra indentation

Output:

Cell In[107], line 3
 print('yayy') # will not work because of extra indentation
 ^
IndentationError: unexpected indent

if block will only be executed if condition, otherwise normal flow will be continued.

Example:

if(2 > 3):
    print('two is less')
print('yayy')

Output:

yayy

If Else¶

if the condition is True, then the if block code will be executed, otherwise else block code will be executed.

Example:

if(2 > 3):
    print('two is greater than 3')
else:
    print('two is not greater than 3')
print('yayy')

Output:

two is not greater than 3
yayy

elif¶

elif is used for checking multiple conditions.

Example:

weather = input('What the weather like? ')
if(weather == 'Sunny'):
    print('Take Googles')
elif (weather == 'Rainy'):
    print('Take Umbrella')
elif (weather == 'Snowy'):
    print('wear boots')
else:
    print('I dont know this weather')
print('normal execution')

else is optional here, it is executed if any of the conditions is not true.

Output 1:

What the weather like? Sunny
Take Googles
normal execution

Output 2:

What the weather like? Mist
I dont know this weather
normal execution

Problem Statement: Traffic Lights¶

You have to ask about the color of the traffic light from the user, if: - it is green, then print go, - it is yellow, then print wait, - it is red, then print stop

green -> go
yellow -> wait
red -> stop

Warning

Please take some time to think about the solution on your own before reading further.....

Solution¶

Code:

light = input()
if (light == 'green'):
    print('go')
elif (light == 'yellow'):
    print('wait')
elif (light == 'red'):
    print('stop')
else:
    print('Wrong input')

Output 1:

green
go

Output 2:

yellow
wait

Output 3:

red
stop

Output 4:

asgsg
Wrong input

Problem Statement: Maximum of two¶

Given two integers, print the maximum of them.

Solution¶

Code:

a = int(input())
b = int(input())
if(a > b):
    print('Maximum of two is', a)
else:
    print('Maximum of two is', b)

Output 1:

100
-100
Maximum of two is 100

Output 2:

12
22
Maximum of two is 22

Problem Statement: Maximum of two and check equality also¶

Given two integers, print the maximum of them or say both are equal.

Solution¶

Warning

Please take some time to think about the solution on your own before reading further.....

Code:

a = int(input())
b = int(input())
if(a == b):
    print('Both numbers are equal')
elif(a > b):
    print('Maximum of two is', a)
else:
    print('Maximum of two is', b)

Output 1:

100
100
Both numbers are equal

Output 2:

12
22
Maximum of two is 22

Problem Statement: Check even or odd¶

Take an integer and print if it is even or odd

Solution¶

Code:

a = int(input())
if(a % 2 == 0):
    print('Number is even')
else:
    print('Number is odd')

Output:

-3
Number is odd

Problem Statement: Print the grade¶

Take marks as input, then print the grade accordingly as given below:

A → (90, 100]
B → (80, 90]
C → (70, 80]
D → [0, 70]

Take it as homework

Problem Statement: FizBuz¶

Given an integer as input: * if it is only a multiple of 3 print only Fizz * if it is only a multiple of 5 print only Buzz * if it is a multiple of both 3 and 5 print Fizz-Buzz

Solution¶

n be a multiple of a if n%a == 0

Code:

a = int(input())
if (a % 3 == 0 and a % 5 == 0):
    print('Fizz-Buzz')
elif (a % 3 == 0):
    print('Fizz')
elif (a % 5 == 0):
    print('Buzz')

Output 1:

15
Fizz-Buzz

Output 2:

27
Fizz

Output 3:

25
Buzz

Output 4:

Question¶

What is the output of the following?

a = 5
if(a < 6):
    print('Option 1')
if(a < 3):
    print('Option 2')
else:
    print('Option 3')

Choices

Option 1
Option 2
Option 3
Option 1
Option 3

a = 5
if(a < 6):
    print('Option 1')
if(a < 3):
    print('Option 2')
else:
    print('Option 3')

If we see in the code,

a = 5
if(a < 6):
    print('Option 1')

if(a < 3):
    print('Option 2')
else:
    print('Option 3')

Both these codes have separate conditions, so in the first condition, it will check for if(a < 6), then again it will check for if(a < 3), and in this case condition will be false, so else will be executed.

Nested if¶

We can have another if inside the if.

Example:

a = input('Is your character Male?')
if(a == 'yes'):
    b = input('Is your character good?')
    if(b == 'yes'):
        print('Your chacter name is chota Bheem')
    else:
        print('Your character name is Kaliya')
else:
    print('Your character name is chutki')

Output 1:

Is your character Male?yes
Is your character good?no
Your character name is Kaliya

Output 2:

Is your character Male?no
Your character name is chutki

Homework: Make a small game over some concept

Operators Hierarchy(Precedence)¶

Operators Precedence In Python.

High precedence operators are calculated first.
For operators with the same precedence will be evaluated from left to right.

Example 1: 3 * 10 / 2

Solution * and / have the same precedence so we will evaluate it from left to right.

= ((3 * 10) / 2) = 30 / 2 = 15

Answer: 15

Example 2: 10 - 5 / 5

Solution

/ have higher precedence than - so first / will be evaluated, then - will be evaluated

= 10 - 1 = 9

Answer: 9

Example 3: 45 % 10 / 2

Solution

% and / have the same precedence so we will evaluate it from left to right.

= ((45 % 10) / 2) = 5 / 2 = 2.5

Answer: 2.5

Example 4: True and not False

Solution

not has higher precedence than and, so first not will be evaluated, then and will be evaluated

= True and (not False) = True and True = True

Answer: True

Example 5: False or not False and True

Solution

not has higher precedence than or and and, so first not will be evaluated, then betweenand and or, and have higher precedence, so and will be evaluated then or will be evaluated.

= False or (not False) and True = False or (True and True) = False or True = True

Answer: True