Complete Course Available at: https://github.com/Ebad8931/PythonWorkshop Basic Concepts of Loops and Conditional Statements in Python are introduced in the presentation. Also covers How to get input from the Console and includes interactive Problems.

1. Instructor: Ebad ullah Qureshi
Email: ebadullah.qureshi@rutgers.edu
N2E Coding Club
Python Workshop
Control Structures
Loops & Conditionals

2. Python workshop by Ebad ullah Qureshi
Recap
2
In the previous lesson
• Introduction to Python Language
• Output of a Program
• Data types – Integer, Floats, Strings
• Variables
• Operators – Arithmetic, Logical, Comparison and Assignment
In this Lesson
• Program Flow – Algorithms

3. Python workshop by Ebad ullah Qureshi
Algorithms and Python Scripts
3
Algorithm is a set of steps used by the computer to solve a problem or accomplish a given task.
Features of algorithms
• Sequencing – Execution of instructions step by step
• Iteration – Using a loop, a block of instruction is executed several times
• Decision Making – Using conditional statements, the set of instructions are either executed or
bypassed
To implement algorithms – Python Scripts are written.
• Python scripts allows several lines of Python to be executed
• Python Scripts are written in a Python IDE
To begin writing a Python script, create a Project and a .PY file in Pycharm.

4. Python workshop by Ebad ullah Qureshi
Getting Input
4
• In python, user is prompted for an input using the input function
• The inputs are always of type string
• The string inputs are converted into different data types when needed
• Python allows multiple inputs at the same time by specifying a delimiter in the split
function

5. Python workshop by Ebad ullah Qureshi
Getting Input – Example
5
# Taking input
major = input("Enter your Major: “)
no_of_credits = int(input("Enter the number of credits you are enrolled in: "))
year, gpa = input("Enter your Year, GPA: ").split(',')
gpa = float(gpa)
print('You are enrolled in ' + year + ' year in ' + major +
' Major. You have currently taken', no_of_credits,
'credits and your GPA is ' + str(gpa))
Enter your Major: Computer Engineering
Enter the number of credits you are enrolled in: 15
Enter your Year, GPA: Junior, 3.58
You are enrolled in Junior year in Computer Engineering Major. You have currently
taken 15 credits and your GPA is 3.58
A Program that takes Major, Number of credits enrolled, GPA, and the Year of study as input and
then displays that information

6. Python workshop by Ebad ullah Qureshi
Discount Price Calculator – Problem
6
Shopping during the sales can sometimes be very
confusing. With discounted prices at 10%, 20%, 50% or
even 70%!
For this challenge you are going to write a Python script
that prompts the user to enter a price (e.g. $90) and a
discount rate to apply (e.g. 20%).
Your program will then calculate and display the full
price, the discounted price and the savings.

7. Python workshop by Ebad ullah Qureshi 7
Discount Price Calculator – Source Code
# Input
price = float(input('Enter the Price of item ($): '))
discount_rate = float(input('Enter the percentage discount (%)'))
# Calculations
savings = price * discount_rate/100
discounted_price = price - savings
# Program Output
print('Original Price: $', price)
print('Discounted Price: $', round(discounted_price, 2))
print('Savings: $', round(savings, 2))

8. Python workshop by Ebad ullah Qureshi
Decision Making – Conditional Statements
8
# simple if statement
test = 67 < 78
if test:
print('logical value of test is True')
logical value of test is True
• Decision making statements controls which instructions to execute in a program
• Decision structures evaluate expressions which produce True or False as the outcome that
dictates which statements to execute
• Python programming language assumes any non-zero and non-null values as TRUE, and
any zero or null values as FALSE value.

9. Python workshop by Ebad ullah Qureshi
Conditional Statements – if…else
9
# simple if-else statement
condition = 24 == 56
if condition:
print('Condition is True')
else:
print('Condition is False')
Condition is False

10. Python workshop by Ebad ullah Qureshi
Conditional Statements – if…elif…else
10
Number is in the range 10 to 19
# if-elif-else statements
number = 12
if (number >= 0) and (number < 10):
print('Number is in the range 0 to 9')
elif (number >= 10) and (number < 20):
print('Number is in the range 10 to 19')
elif (number >= 20) and (number < 30):
print('Number is in the range 20 to 29')
else:
print('Number is negative or greater than 29')

11. Python workshop by Ebad ullah Qureshi 11
Printing multiple times I
print('Hello World')
print('Hello World')
print('Hello World')
print('Hello World')
print('Hello World')
Print out ‘Hello world’ 5 times
Problem in the above code: Repetition of same code
• To achieve this, programming languages use control structures called loops.
• One cycle of a loop is called iteration
• Loops avoid repeated statements and are useful when the number of iterations depend upon
user’s input

12. Python workshop by Ebad ullah Qureshi
Loops – loop variables
12
Loop initial value – Specifies the starting value of the loop
Loop end value – Specifies the end value of the loop
Body of the Loop – Statements inside the loop
Loop Condition – Logical value that dictates whether to execute the body of the loop or to exit
out of the loop
Loop Counter – The loop variable that tracks the number of iterations and the current iteration
Loop increment/decrement – The value by which the loop counter increases or decreases in each
iteration

13. Python workshop by Ebad ullah Qureshi
Loops – For Loop
13
for loop_counter in range(loop_initial_value, loop_end_value, loop_increment):
Statements of the loop body.
End of loop body
• In a for loop, the number of iterations are specified. They can be known or unknown to the
programmer
• The default loop_initial_value is 0
• The default loop_increment is 1
• Loop terminates when loop_counter is equal to (or gets greater than) the loop_end_value

14. Python workshop by Ebad ullah Qureshi
Loops – While Loop
14
loop_counter = loop_initial_value
while loop_condition:
Statements of the loop body.
End of loop body
loop_counter = loop_increment
• In a while loop, the number of iterations are dependent on the loop condition
• The number of iterations in a while loop can be known or unknown to the programmer

15. Python workshop by Ebad ullah Qureshi
Printing multiple times II
15
The Problem about printing “Hello World” 5 times can be efficiently coded using loops.
The Loop body would be: print(‘Hello World’)
# for loop
for i in range(5):
print('hello world')
# while loop
count = 0
while count < 5:
print('hello world')
count += 1
 The loop body is executed 5 times
 loop_initial_value = 0
 loop_increment = 1
 To terminate the loop in case of a for loop →
loop_end_value = 5
 To terminate the while loop →
loop_condition = loop_counter < 5
 In both cases, Loop would run for the following values
of loop_counter: 0, 1, 2, 3, 4

16. Python workshop by Ebad ullah Qureshi
Break & Continue
16
for i in range(5, 10):
print(i)
if i == 8:
break # Break Statement: Program exits out of the loop
5
6
7
8
for i in range(5, 10):
if i == 7 or i == 8:
continue # Continue Statement: skip certain iterations
print(i)
5
6
9

17. Python workshop by Ebad ullah Qureshi
Staircase – Problem
17
Consider a staircase of size: n = 10
Observe that its base and height are both equal to , and the image is drawn
using # symbols and spaces. The last line is not preceded by any spaces.
Write a program that prints a staircase of size .
Input Format
A single integer, , denoting the size of the staircase.
Constraints
0 < n ≤ 100
Output Format
Print a staircase of size using # symbols and spaces.
Explanation
The staircase is right-aligned, composed of # symbols and
spaces, and has a height and width of n = 10.

18. Python workshop by Ebad ullah Qureshi
Staircase - Approach
18
#
# #
# # #
# # # #
# # # # #
# # # # # #
# # # # # # #
# # # # # # # #
# # # # # # # # #
# # # # # # # # # #
Observations
input n = number of lines
Iterate through each line such that
 line number (starting from 0) = loop counter
In each line for 10 lines
 number of whitespaces = 9 - loop counter
 number of symbols = loop counter + 1
In each line for n lines
 number of whitespaces = n-1 - loop counter
 number of symbols = loop counter + 1

19. Python workshop by Ebad ullah Qureshi
Staircase – Source Code
19
lines = int(input('Enter the number of lines to be displayed: '))
for i in range(lines):
print((lines-1-i)*' ' + '#'*(i+1))
Enter the number of lines to be displayed: 5
#
##
###
####
#####

20. Python workshop by Ebad ullah Qureshi
Further Exploration – Try these Patterns
20

21. Instructor: Ebad ullah Qureshi
Email: ebadullah.qureshi@rutgers.edu
N2E Coding Club
Python Workshop
Control Structures
Complete