Loops in Python Programming
Loops in python
programming
➔
For
➔
while
Outline
1.
For loop
2.
Range function
3.
Break, continue, and Pass
statement
4.
Booleans
5.
While loop
6.
Nested loop
For Loop
The
for
loop in python iterates over the items of any
sequence be it a list or a string. Moreover, using
for
loop in
the program will minimize the line of code.
Points to keep in mind while using
for
loop in python:
➔
It should always start with for keyword and should
end with a colon(:).
➔
The statements inside the loop should be
indented(four spacebars).
S
y
n
t
a
x
:
For iterator_variable in sequence:
statement(s)
Example
Code:
for i in range(6):
print(“Hello World!”)
Output:
print(“Hello World!”)
print(“Hello World!”)
print(“Hello World!”)
print(“Hello World!”)
print(“Hello World!”)
This is actually a temporary
variable which store the
number of iteration
Number of times you want to
execute the statement
Range function
To iterate over a sequence of numbers, the built-in function
range() comes in handy. It generates arithmetic
progressions. For example, if we want to print a whole
number from 0 to 10, it can be done using a range(11)
function in a for loop.
In a range() function we can also define an optional start
and the endpoint to the sequence. The start is always
included while the endpoint is always excluded.
E
x
a
m
p
l
e
:
for i in range(1, 6):
print("Hello World!")Output:
Prints Hello World! five times
Starting point
Ending point
Range function
The range() function also takes in another optional
parameter i.e. step size. Passing step size in a range()
function is important when you want to print the value
uniformly with a certain interval.
Step size is always passed as a third parameter where the
first parameter is the starting point and the second
parameter is the ending point. And if the step_size is not
provided it will take 1 as a default step_size.
E
x
a
m
p
l
e
:
for i in range(0,20, 2):
print(i)
Output:
prints all the even numbers till 20
Step size
c
o
n
t
…
.
Sum of numbers
-Write a program to find the sum of all the numbers less than
a number entered by the user. Display the sum.
Expected Output:
1
Break, Continue, & Pass Statement
(Loop control statement)
➔
A
break
statement is used to immediately terminate
a loop.
➔
A
continue
statement is used to skip out future
commands inside a loop and return to the top of the
loop.
➔
A
Pass
is a null operation — when it is executed,
nothing happens. It is useful as a placeholder when a
statement is required syntactically when no code
needs to be executed.
➔
These statements can be used with for or while loops.
Break, Continue, & Pass Statement
(Loop control statement)
Example:
Magic Number
Write a program that makes the user guess a particular
number between 1 and 100. Save the number to be
guessed in a variable called magic_number.
If the user guesses a number higher than the secret
number, you should say
Too high!
. Similarly, you should
say
Too low!
if they guess a number lower than the secret
number. Once they guess the number, say
Correct!
Expected Output:
2
Boolean
A boolean is a value that can be either True or False.
E
x
a
m
p
l
e
:
brought_food =
True
brought_drink =
False
-
Boolean variables don't have quotation marks.
-
The values must start with capital letters.
While Loop
➔
while loop repeatedly carries out a target statement while the condition is
true. The loop iterates as long as the defined condition is True.
➔
When the condition becomes false, program control passes to the line
immediately following the loop.
E
x
a
m
p
l
e
:
while True:
print("I am a programmer")break
while False:
print("Not printed because while the condition is already False")break
Output:
I am a programmer
While Loop
Example:
x = 1
while x > 0:
print ("Hello!")x = x - 1
print ("I like Python.")Output:
Hello!
I like Python.
Guess the number
Write a program where the user enters a
number. If the number matches the number,
acknowledge the user and stop the program. If
the number does not match, keep asking for the
next number.
Expected Output:
3
Nested Loop
Loop within a loop is called a nested loop.
➔
For loop within for loop is called a
nested for loop.
➔
While loop within while loop is called as
nested while
loop.
Nested Loop(Example)
for i in range(4):
x = 5
while x > 1:
print (x)
x = x - 1
O
u
t
p
u
t
:
5
4
3
2
5
4
3
2
5
4
3
2
5
4
3
2
Rolling a dice
Write a program that will print out all combinations that can
be made when 2 dice are rolled. And should continue until
all values up to 6, and 6 are printed. (Hint: You should have a
space after each comma!)
Expected Output:
4
Multiplication Table:
Write a program to print a multiplication
table to 12 of a given number.
Expected Output:
1
Printing pattern:
Write a program to print the following two
patterns implementing the nested loop
concept.
2
The concept of loops in Python programming is explained in detail, covering for and while loops, the range function, break, continue, and pass statements, and examples to demonstrate their usage. Learn how to iterate over sequences, handle loop control statements, and efficiently execute repetitive tasks using loops in Python.
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Presentation Transcript
Loops in python programming For while
1. For loop 2. Range function 3. Break, continue, and Pass statement 4. Booleans 5. While loop 6. Nested loop Outline
For Loop The for loop in python iterates over the items of any sequence be it a list or a string. Moreover, using for loop in the program will minimize the line of code. Points to keep in mind while using for loop in python: It should always start with for keyword and should end with a colon(:). The statements inside the loop should be indented(four spacebars). Syntax: For iterator_variable in sequence: statement(s)
Example This is actually a temporary variable which store the number of iteration Code: for i in range(6): print( Hello World! ) Number of times you want to execute the statement Output: print( Hello World! ) print( Hello World! ) print( Hello World! ) print( Hello World! ) print( Hello World! )
Range function To iterate over a sequence of numbers, the built-in function range() comes in handy. It generates arithmetic progressions. For example, if we want to print a whole number from 0 to 10, it can be done using a range(11) function in a for loop. In a range() function we can also define an optional start and the endpoint to the sequence. The start is always included while the endpoint is always excluded. Starting point Example: Ending point for i in range(1, 6): print("Hello World!") Output: Prints Hello World! five times
cont. Range function The range() function also takes in another optional parameter i.e. step size. Passing step size in a range() function is important when you want to print the value uniformly with a certain interval. Step size is always passed as a third parameter where the first parameter is the starting point and the second parameter is the ending point. And if the step_size is not provided it will take 1 as a default step_size. Step size Example: for i in range(0,20, 2): print(i) Output: prints all the even numbers till 20
1 Sum of numbers -Write a program to find the sum of all the numbers less than a number entered by the user. Display the sum. Expected Output:
Break, Continue, & Pass Statement (Loop control statement) A break statement is used to immediately terminate a loop. A continue statement is used to skip out future commands inside a loop and return to the top of the loop. A Pass is a null operation when it is executed, nothing happens. It is useful as a placeholder when a statement is required syntactically when no code needs to be executed. These statements can be used with for or while loops.
Break, Continue, & Pass Statement (Loop control statement) Example: Break Continue Pass for i in range(10): if i == 3: break print(i) for i in range(5): if i == 3: continue print(i) Output: 0 1 2 4 for i in range(10): Pass Output: 0 1 2 Output: Nothing will be printed
2 Magic Number Write a program that makes the user guess a particular number between 1 and 100. Save the number to be guessed in a variable called magic_number. If the user guesses a number higher than the secret number, you should say Too high!. Similarly, you should say Too low! if they guess a number lower than the secret number. Once they guess the number, say Correct! Expected Output:
Boolean A boolean is a value that can be either True or False. Example: brought_food = True brought_drink = False - - Boolean variables don't have quotation marks. The values must start with capital letters.
While Loop while loop repeatedly carries out a target statement while the condition is true. The loop iterates as long as the defined condition is True. When the condition becomes false, program control passes to the line immediately following the loop. Example: while True: print("I am a programmer") break while False: print("Not printed because while the condition is already False") break Output: I am a programmer
While Loop Example: x = 1 while x > 0: print ("Hello!") x = x - 1 print ("I like Python.") Output: Hello! I like Python.
3 Guess the number Write a program where the user enters a number. If the number matches the number, acknowledge the user and stop the program. If the number does not match, keep asking for the next number. Expected Output:
Nested Loop Loop within a loop is called a nested loop. For loop within for loop is called a nested for loop. While loop within while loop is called as nested while loop. Example: Nested for loop Example: Nested while loop for i in range(4): for j in range(3): print ("Hello!") i = 1 j = 5 while i < 4: while j < 8: print(i,",", j) j = j + 1 j i = i + 1
Nested Loop(Example) Output: 5 4 3 2 5 4 3 2 5 4 3 2 5 4 3 2 for i in range(4): x = 5 while x > 1: print (x) x = x - 1
4 Rolling a dice Write a program that will print out all combinations that can be made when 2 dice are rolled. And should continue until all values up to 6, and 6 are printed. (Hint: You should have a space after each comma!) Expected Output:
1 Multiplication Table: Write a program to print a multiplication table to 12 of a given number. Expected Output:
2 Printing pattern: Write a program to print the following two patterns implementing the nested loop concept.
