Python format() Method

The Python format() function is a built-in that returns a formatted string representation of a given value according to a specified format specification. As a string method, str.format() accepts one or more positional or keyword arguments that are inserted into placeholder positions marked by curly braces {} within the string. Placeholders can use positional indexes like {0}, keyword names like {name}, or remain empty for sequential filling. The format specification mini-language supports alignment, padding, sign handling, width, precision, and type codes for integers, floats, percentages, and more. The function returns a new formatted string. A common real-world use case is generating formatted output for reports, receipts, and dashboards where numbers need specific decimal precision, currency formatting, or column alignment.

What does format() return?

The format() method returns a new string where the placeholder fields are replaced with the formatted values of the provided arguments.

When should you use format()?

Use format() when you need to construct strings with dynamic values and specific formatting requirements, such as controlling decimal places, padding, alignment, or converting numbers to binary, hex, or percentage representations.

Common Use Cases

A frequent use of format() is generating user-facing output with consistent number formatting, such as displaying prices with exactly two decimal places using "{:.2f}".format(price). Another practical scenario is creating aligned table output in command-line tools, where fixed-width format specifiers ensure columns line up properly. It is also commonly used in logging and debugging to construct descriptive messages with variable data. Related functions include the Python float() method for converting values before formatting and the Python eval() method for dynamic expression evaluation, though format() is always the safer choice for string interpolation.

What is python format() method?

The format() is a built-in pythonmethod that returns a formatted representation of the specified value.

The syntax of format() is:

format(value1, value2)

format() Parameters

The format()methods takes single parameters but multiple arguments:

• values - one or more values that needed to be formatted.

format() Placeholders

The placeholders can be identified using names indexes {value}, numbered indexes like {0} , {1},etc. Or even empty {} placeholder.

Let’s check a simple example of the format()method.

Example 1: Simple formatting using format() method.

my_string = "Python"

print("We are learning {} from Pythonscholar.com".format("Python"))

print("We are learning {} from Pythonscholar.com".format(my_string))

print("We are learning {1} from {0}".format("Pythonscholar.com","Python"))

Output:

We are learning Python from Pythonscholar.com
We are learning Python from Pythonscholar.com
We are learning Python from Pythonscholar.com

Formatting Specifiers

format() method also supports different types for formatting specifiers that helps to manipulate the results.

:<	Result will be aligned left
:>	Result will be aligned right
:^	Result will be aligned center
:=	Places the sign to the left most position
:+	Use a plus sign to indicate if the result is positive or negative
:-	Use a minus sign for negative values only
:	Use a space to insert an extra space before positive numbers (and a minus sign before negative numbers)
:,	Use a comma as a thousand separator
:_	Use a underscore as a thousand separator
:b	Binary format
:c	Converts the value into the corresponding unicode character
:d	Decimal format
:e	Scientific format, with a lowercase e
:E	Scientific format, with an uppercase E
:f	Fix point number format
:F	Fix point number format, in uppercase format (show inf and nan as INF and NAN)
:g	General format
:G	General format (using a upper case E for scientific notations)
:o	Octal format
:x	Hex format, lower case
:X	Hex format, upper case

:n	Number format
:%	Percentage format

Example 2: Using format specifiers with format() method.

print("The value is : {:x}".format(500))
print("The value is : {:%}".format(0.80))
print("The value is: {:5}".format(40))

Output:

The value is : 1f4
The value is : 80.000000%
The value is:    40

Rules of format()

There are no such rules to follow in the format() method.