Python If-else and elif
statements
Decision making
is the most important aspect of almost all the programming languages. As the
name implies, decision making allows us to run a particular block of code for a
particular decision. Here, the decisions are made on the validity of the
particular conditions. Condition checking is the backbone of decision making.
Eg: Program to
print the largest of the three numbers.
a =
int(input("Enter a? "));
b =
int(input("Enter b? "));
c =
int(input("Enter c? "));
if a>b and
a>c:
print("a is largest");
if b>a and
b>c:
print("b is largest");
if c>a and
c>b:
print("c is largest");
>>>Output
Enter a? 100
Enter b? 120
Enter c? 130
c is largest
>>>Program
to check whether a person is eligible to vote or not.
age = int
(input("Enter your age? "))
if
age>=18:
print("You are eligible to vote !!");
else:
print("Sorry! you have to wait !!");
>>>Output
Enter your age?
90
You are eligible
to vote !!
The elif
statement
The elif
statement enables us to check multiple conditions and execute the specific
block of statements depending upon the true condition among them. We can have
any number of elif statements in our program depending upon our need. However,
using elif is optional.
The elif
statement works like an if-else-if ladder statement in C. It must be succeeded
by an if statement.
The syntax of
the elif statement is given below:
Eg:
if expression
1:
#
block of statements
elif expression
2:
#
block of statements
elif expression
3:
#
block of statements
else:
#
block of statements
Python for loop
The for loop in Python is used to iterate
the statements or a part of the program several times. It is frequently used to
traverse the data structures like list, tuple, or dictionary.
The syntax of for loop in python is given below.
for iterating_var in sequence:
statement(s)
Eg:
i=1;
num = int(input("Enter
a number:"));
for i in range(1,11):
print("%d
X %d = %d"%(num,i,num*i));
>>>Output:
Enter a number:10
10 X 1 = 10
10 X 2 = 20
10 X 3 = 30
10 X 4 = 40
10 X 5 = 50
10 X 6 = 60
10 X 7 = 70
10 X 8 = 80
10 X 9 = 90
10 X 10 = 100
Nested for loop
in python
Python allows us to nest any
number of for loops inside a for loop. The inner loop is executed n number of
times for every iteration of the outer loop. The syntax of the nested for loop
in python is given below.
for iterating_var1 in
sequence:
for
iterating_var2 in sequence:
#block
of statements
#Other statements
Example 1
n = int(input("Enter
the number of rows you want to print?"))
i,j=0,0
for i in range(0,n):
print()
for
j in range(0,i+1):
print("*",end="")
>>>Output:
Enter the number of rows you
want to print?5
*
**
***
****
*****
Using else
statement with for loop
Unlike other languages like
C, C++, or Java, python allows us to use the else statement with the for loop
which can be executed only when all the iterations are exhausted. Here, we must
notice that if the loop contains any of the break statement then the else
statement will not be executed.
Example 1
for i in range(0,5):
print(i)
else:print("for loop
completely exhausted, since there is no break.");
In the above example, for
loop is executed completely since there is no break statement in the loop. The
control comes out of the loop and hence the else block is executed.
>>>Output:
0
1
2
3
4
Python while loop
The while loop is also known as a pre-tested loop. In
general, a while loop allows a part of the code to be executed as long as the
given condition is true.
It can be viewed as a repeating if statement. The while loop
is mostly used in the case where the number of iterations is not known in
advance.
The syntax is given below.
while expression:
statementsExample
1
i=1;
while i<=10:
print(i);
i=i+1;
>>>Output:
1
2
3
4
5
6
7
8
9
10
Example 2
i=1
number=0
b=9
number =
int(input("Enter the number?"))
while i<=10:
print("%d
X %d = %d \n"%(number,i,number*i));
i =
i+1;
>>>Output:
Enter the number?10
10 X 1 = 10
10 X 2 = 20
10 X 3 = 30
10 X 4 = 40
10 X 5 = 50
10 X 6 = 60
10 X 7 = 70
10 X 8 = 80
10 X 9 = 90
10 X 10 = 100
Using else with Python while
loop
Python enables us to use the
while loop with the while loop also. The else block is executed when the
condition given in the while statement becomes false. Like for loop, if the
while loop is broken using break statement, then the else block will not be executed
and the statement present after else block will be executed.
Consider the following
example.
i=1;
while i<=5:
print(i)
i=i+1;
else:print("The while
loop exhausted");
>>>Output:
1
2
3
4
5
The while loop exhausted
Python continue
Statement
The continue statement in
python is used to bring the program control to the beginning of the loop. The
continue statement skips the remaining lines of code inside the loop and start
with the next iteration. It is mainly used for a particular condition inside
the loop so that we can skip some specific code for a particular condition.
The syntax of Python
continue statement is given below.
#loop statements
continue;
#the code to be
skipped
Example 1
i = 0;
while i!=10:
print("%d"%i);
continue;
i=i+1;
>>>Output:
infinite loop
Example 2
i=1; #initializing a local
variable
#starting a loop from 1 to
10
for i in range(1,11):
if
i==5:
continue;
print("%d"%i);
>>>Output:
1
2
3
4
6
7
8
9
10
Python Pass
In Python, pass keyword is
used to execute nothing; it means, when we don't want to execute code, the pass
can be used to execute empty. It is same as the name refers to. It just makes
the control to pass by without executing any code. If we want to bypass any
code pass statement can be used.
Python Pass Syntax
pass
Python Pass Example
for i in [1,2,3,4,5]:
if
i==3:
pass
print
"Pass when value is",i
print
i,
>>>Output:
1 2 Pass when value is 3
3 4 5
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