Now we are going to step into looping concepts in python.
When you want to do a job repeatedly, you need to put the
instructions under a loop. The loops available with python are :
-
while loop
-
for loop
Python does not have a do-while loop. Today we will look into
'while-loops'.
While-loop in Python:
Syntax:
initialize loop control variable
while condition:
statement 1
statement 2
.
.
.
statement n
First we need to initialize the 'loop control variable'. It is
nothing but the value of variable on which the whole loop is going
to be dependent. Here also we do not have curly braces. The
indentation only matters.
Example 1: Print the numbers from 1 to 10
Here I have checked the condition as 'while i<11:', because You need to print the number '10' also. Thus we take one
excess.
Note that if you fail to give the incremental part, then the
loop will become an infinite one.
#Printing hacks in Python
How to print on the same line !?
Just write as given below:
In the print statement add end=" ". This will leave a space after each printed element instead of
adding a new line.
Example 2: Get a range from the user and print the numbers in that range:
Example 3: Can we do decremental steps in the loop ? Look at the code below. Let us print the numbers in given range in reverse.
Nested While-loops:
We can nest the while loops as we did in if-else conditions. When
you nest the loops, the innermost loop is executed until its
condition fails. Then the nearest outer loop will be executed.
Example 4:
Consider the most frequently asked placement problem : Pattern
Printing. You might be asked to print a pattern like this:
*
**
***
****
*****
Code:
Example 5:
Now lets us code for finding sum of digits in a number. These are also a kind of placement problems. These can be asked in interviews.
Consider a 5 digit number - 23764. The sum is 2+3+7+6+4=22
What we do here is :
First we do modulo division with 10, so that we can get the last
number as reminder every time. It is added with 't'. We save the
quotient of the number back to 'i'. Now take a look at each
iteration:
Iteration 0:
i=45767
t=0
Iteration 1:
t+=i%10------- 45767%10=7
Thus t=7
i=i//10--------45767//10=4576
**Here we use '//' for division because we need an integer as output
and not a floating number. This yields the integer value.
Iteration 2:
t+=i%10------4576%10= 7+6 =13
t=13
i=4576//10 = 457
Iteration 3:
t+=7
t=20
i=45
Iteration 4:
t+=5
t=25
i=4
Iteration 5:
t+=4
t=29
i=0
thus the answer is 29.
Exercise:
1. Get input 'n' from the user , find the product of numbers
from 1 to n.
2. Try printing the pattern below:
1
22
333
4444
55555
666666
7777777
88888888
999999999
Next Topic👉
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