String Interpolation in Python

September 12, 2023

String Interpolation

String interpolation is a process of injecting value into a placeholder (a placeholder is nothing but a variable to which you can assign data/value later) in a string literal. It helps in dynamically formatting the output in a fancier way. Python supports multiple ways to format string literals.

Ways of String Interpolation

%-formatting
str.format()
Template Strings
F-strings

%-formatting –

In python modulo(%) operator is overloaded in str class to perform string formatting.
If we have lots of variable to concat , then we can use %-formatting.

code 1:

Run

# Python program to demonstrate 
# string interpolation 
n1 = 'Hello'
n2 ='PrepInsta'
# for single substitution 

print("Welcome to % s"% n2) 
n3='Prepsters'
# for single and multiple substitutions () mandatory 
print("% s % s welcome to %s."%(n1, n3,n2))

Output:

Welcome to PrepInsta
Hello Prepsters welcome to PrepInsta.

Str.format()

It is one of the string formatting methods in Python3.
It is used for positional formatting, this allows re-arranging the order of placeholders within string literals without changing the order they are listed in .format( ).

Code 2:

Run

# Python program to demonstrate 
# string interpolation 
n1 = 'Hello'
n2 ='PrepInsta'
# for single substitution 
print("Welcome to {}" .format(n2)) 
n3='Prepsters'
# for multiple substitutions  
print("{b1} {b2} welcome to {b3}.".format(b1=n1, b2=n3,b3=n2))

Output:

Welcome to PrepInsta
Hello Prepsters welcome to PrepInsta.

Template Strings

It lets you make substitutions in a string using a mapping object.
Here, a valid python identifier preceded by sign ‘$’ is used as a placeholder.

Code 3:

Run

# Python program to demonstrate 
# string interpolation 
from string import Template 
n1 = 'Hello'
n2 ='PrepInsta'
# made a template which we can we use
p=Template('Welcome to $s2')
print(p.substitute(s2=n2))
n3='Prepsters'
p1=Template('$s1 $s2 Welcome to $s3.')
print(p1.substitute(s1=n1, s2=n3,s3=n2))

Output:

Welcome to PrepInsta
Hello Prepsters Welcome to PrepInsta.

F-strings

F-strings provide a way to embed expressions inside string literals, using a minimal syntax.
In Python source code, an f-string is a literal string, prefixed with ‘f’, which contains expressions inside braces.

Code 4:

Run

# Python program to demonstrate 
# string interpolation 
from string import Template 
n1 = 'Hello'
n2 ='PrepInsta'
# for single substitution 
print(f"Welcome to {n2}")
n3='Prepsters' 
print(f"{n1} {n3} welcome to {n2}.")

Output:

Welcome to PrepInsta
Hello Prepsters welcome to PrepInsta.

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Slicing with Negative Numbers

Using Step In a Slicing

String Operators in Python

String Replacement Fields in Python

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String Interpolation in Python