String Interpolation in Python

String interpolation is a powerful approach utilized in Python to create dynamic and flexible strings. It helps to embed variables, expressions, or even capabilities within a string literal which helps to generate complex and noticeably customizable output. Python has multiple string interpolation methods, such as `%`-based format strings, `str.Format()`, f-strings, and the template class. Knowing these methods will help you utilize Python's string interpolation capabilities to write clean, concise, and maintainable code.

This article will let you explore the concept of string interpolation, its uses, features, methods, and implementation in Python.

More About String Interpolation in Python

String interpolation in Python refers to the manner of embedding variables or expressions inside a string to create a new string.

String interpolation enables dynamic substitution and has two parts:

• String Template
• Value

The values are meant to be stored in the string template, while the interpolation of strings. It needs some methods to add values to the string template. There are four methods for string interpolation. Each method has its own merits and demerits; we will learn about every method in-depth, along with its implementation.

The methods of string interpolation are as follows:

1. Modulo character (%): The string can be replaced using the modulo % character. It can be added within a string literal followed by the string format indicators and variables.
2. .format( ): This method can be called on the string literal. The string replacement can be indicated by the curly braces { }, which are inserted with the string. The parameters of the .format( ) method represent the value used for the replacement of the string.
3. f-string: Formatted string literals can be used just by applying the letter f before the string letter. The curly braces { } can be used to delimit Python string and replace it.
4. Template Class: The built-in template class can also be used for string interpolation. The template( ) stores the string template in a variable. And the .subsitute( ) function is used for the string substitution.

Let's dig into the detailed knowledge of these techniques.

Modulo Operator for String Formatting

The module operator is used for string interpolation and formatting. The formatting with the modulo operator uses the % character along with the format indicator, which indicates the type of entry in the string template. The format indicator tries to change the value into the value provided in the modulo function. The formatting is done before any value is added to the string.

The basic syntax of using the modulo operator for string interpolation is:

Syntax:

%[flg] [width] [.precision] format_indicator %(values)

The format indicators used with the modulo functions are:

• %s: String
• %d: Integer
• %e: Lowercase exponent
• %E: Uppercase exponent
• %x: Lowercase hexadecimal
• %X: Uppercase hexadecimal
• %r: Raw
• %c: Returns character (converted from int or char)
• %a: ASCII
• %o: Octal
• %f: Floating Numbers

It basically interpolates variables into strings. While %-formatting remains supported in Python, it's considered less favorable due to its complexity and limited capabilities compared to newer methods.

Now, we will learn this method of string interpolation using a few examples in Python.

Code:

Output:

Hey, I am Tom and I am 22 years old.

String Interpolation using the .format( ) method

This is another method for string interpolation. It uses the str.format( ) method for the same. The .format() method, available in earlier Python versions, offers a flexible approach to string formatting. It allows for positional and keyword arguments, enhancing string customization. The .format( ) method provides a versatile way to incorporate variables and expressions into strings. Its syntax involves using placeholders within a string and then providing values through the .format( ) function.

It can be used with the string objects in Python. Curly braces { } are used with the parameters of the .format( ) method in Python. It may consist of a numeric index or positional argument, etc.

Here's a close look and explanation of the .format( ) method used for string interpolation in Python:

The .format() method employs placeholders, represented by curly braces {}, within a string. These placeholders act as slots where values can be inserted. The method allows for positional or keyword arguments, offering flexibility in passing values to placeholders. Positional arguments correspond to the order of placeholders, while keyword arguments specify placeholders by name.

Now, let's see an example to learn the .format( ) method in Python:

Code:

Output:

Hey, I am Tom and I am 22 years old.

Interpolating String with f-string

Another beneficial technique for interpolating strings is with the aid of the usage of f-string. It also can be called formatted string literals. F-strings were brought in Python 3.6, providing a concise and green manner to embed expressions at once within strings. They offer simplicity and readability in code. It can be referred to as through the use of f or F before the variables of the string enclosed with the curly braces.

F-strings allow direct referencing of variables and expressions within strings, making the code more readable and briefer compared to other interpolation methods.

Let's explore the use of f-string using examples in Python.

Code:

Output:

Hey, I am Tom and I am 22 years old.

String Interpolation using Template Class

Template class is a sub-module in the String module. It is used for the substitution of strings. However, we can not format strings with the use of this method. This technique of string interpolation is secure in comparison with different techniques.

The str.Template magnificence operates by growing template strings with placeholders identified through dollar symbol and enclosed in curly braces '$ { }'. The $ is used earlier than the call of the variable or character, that's handed as an issue to the Template class. The substitute() method replaces placeholders inside the template string with values surpassed as keyword arguments, offering a secure and clear manner for string interpolation.

Let's understand the concept of Template class for string interpolation using an example in Python:

Code:

Output:

Hey, I am Tom and I am 22 years old.