Day 3 : Conditional and looping statements

Hello guys, 

Here we are, Day 3🤟

Some of you are beginner and some of you have basic knowledge and understanding of python or any programming language. 

Each and every language have their own syntax. 

Previously on Day 2, we learn about variables, keywords, datatypes and operators. 

Let's dive into 

Conditional Statemts :

Quick Note :

Python relies on indentation (whitespace at the beginning of a line) to define scope in the code. Other programming languages often use curly-brackets {} for this purpose.

1] if statement :

If condition is true then block will execute. 

Syntax:

if <condition>:
    <statement>

In the form shown above:

1. <condition> is an expression evaluated in Boolean context, as discussed in the section on Logical Operators in the Operators and Expressions in Python tutorial.

2. <statement> is a valid Python statement, if <expr>:

    <statement> must be indented. 

Example:

2] if-else statement

If condition is true then only if block will execute and else block will  skipped

If condition is false then else block will execute and if block will skipped. 

Syntax:

if <condition>:
    <statement(s)>
else:
    <statement(s)>

Example:

 1 >>> x = 20
 2 
 3 >>> if x < 50:
 4 ...     print('first suite')
 5 ...     print('x is small')
 6 ... else:
 7 ...     print('second suite')
 8 ...     print('x is large')
 9 ...
10 first suite
11 x is small

3]elif statement:

This is if-elif statement, 

In this if condition false then we can check for another condition if that condition is also get false then we can check for condition and so on at the end else block will execute if no conditions satisfied. In some language it is called as if-else ladder. 

Here we check for multiple conditions. 

Syntax

if <condition1>:
    <statement(s)>
elif <condition2>:
    <statement(s)>
elif <condition3>:
    <statement(s)>
    ...
else:
    <statement(s)>

Example

>>> name = 'Joe'
>>> if name == 'Fred':
...     print('Hello Fred')
... elif name == 'Xander':
...     print('Hello Xander')
... elif name == 'Joe':
...     print('Hello Joe')
... elif name == 'Arnold':
...     print('Hello Arnold')
... else:
...     print("I don't know who you are!")
...
Hello Joe

Looping statements:

1] While Loop

In this, loop will execute until condition is true. 

Here expressions mean condition. 

Syntax:

while expression:
    statement(s)

Example

count = 0

while (count < 3):    

    count = count+1

    print("Hello") 

Output

Hello 
Hello 
Hello

2] for Loop

For Loop is different from other languages for loop. 

I. E. for (i=0; i<n; i++). 

Sequence may be list or tuple or set or string. 

Syntax

for iterator_var in sequence:
    statements(s)

for iterator_var in range(number):
    statements(s)

 Example

l= ["Welcome", "To", "Pyworld"]

for i in l:

    print(i)

Output

Welcome
To
Pyworld

3] Nested loop

Simply means loop within loops. 

Syntax

for iterator_var in sequence:
    for iterator_var in sequence:
        statements(s)
        statements(s)

while expression:
    while expression: 
        statement(s)
        statement(s)

Example

for i in range(1, 5):

    for j in range(i):

         print(i, end=' ')

    print() 




Output

1
2 2
3 3 3
4 4 4 4

Control Statemts

1] Continue Statement

It returns the control to the beginning of the loop.

Example

for letter in 'hello': 

    if letter == 'e' or letter == 'l':

         continue

    print('Current Letter :'+ letter) 

Output

Current Letter : h

Current Letter : o

2] Break Statement

It brings control out of the loop

Example

for letter in 'hello': 

    if  letter == 'l':

         break

    print('Current Letter :'+ letter) 

Output

Current Letter : h

Current Letter : e

3] Pass Statement

We use pass statement to write empty loops. Pass is also used for empty control statement, function and classes.

Example

for letter in 'hello': 

    pass

print('Last Letter :'+ letter) 

Output

Last Letter : o

Task 

Quick note:

These tasks are for you. 

Don't cheat or copy paste code. You don't learn anything from that. 

Just be honest to yourself. 

If you stuck somewhere just ask in group, other people will help you for sure. 

Take challenge😉👍

Try to do this within 2 hours. 🤟

Easy

1] Even or odd number

2] Armstrong number

3] Positive negative or zero

Medium

1] Factorial of number

2] Reverse strings without using built-in function. 

Hard

1] all prime numbers from 1 to 100 (without using function) 

Pattern programs. 



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