Python String Formatting

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F-String was introduced in Python 3.6, and is now the preferred way of formatting strings.

Before Python 3.6 we had to use the format() method.

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F-Strings

F-string allows you to format selected parts of a string.

To specify a string as an f-string, simply put an f in front of the string literal, like this:

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Placeholders and Modifiers

To format values in an f-string, add placeholders {}, a placeholder can contain variables, operations, functions, and modifiers to format the value.

A placeholder can also include a modifier to format the value.

A modifier is included by adding a colon : followed by a legal formatting type, like .2f which means fixed point number with 2 decimals:

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You can also format a value directly without keeping it in a variable:

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Perform Operations in F-Strings

You can perform Python operations inside the placeholders.

You can do math operations:

You can perform math operations on variables:

You can perform if...else statements inside the placeholders:

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Execute Functions in F-Strings

You can execute functions inside the placeholder:

The function does not have to be a built-in Python method, you can create your own functions and use them:

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More Modifiers

At the beginning of this chapter we explained how to use the .2f modifier to format a number into a fixed point number with 2 decimals.

There are several other modifiers that can be used to format values:

Here is a list of all the formatting types.

Formatting Types
:<	Try it	Left aligns the result (within the available space)
:>	Try it	Right aligns the result (within the available space)
:^	Try it	Center aligns the result (within the available space)
:=	Try it	Places the sign to the left most position
:+	Try it	Use a plus sign to indicate if the result is positive or negative
:-	Try it	Use a minus sign for negative values only
:	Try it	Use a space to insert an extra space before positive numbers (and a minus sign before negative numbers)
:,	Try it	Use a comma as a thousand separator
:_	Try it	Use a underscore as a thousand separator
:b	Try it	Binary format
:c		Converts the value into the corresponding Unicode character
:d	Try it	Decimal format
:e	Try it	Scientific format, with a lower case e
:E	Try it	Scientific format, with an upper case E
:f	Try it	Fix point number format
:F	Try it	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	Try it	Octal format
:x	Try it	Hex format, lower case
:X	Try it	Hex format, upper case
:n		Number format
:%	Try it	Percentage format

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String format()

Before Python 3.6 we used the format() method to format strings.

The format() method can still be used, but f-strings are faster and the preferred way to format strings.

The next examples in this page demonstrates how to format strings with the format() method.

The format() method also uses curly brackets as placeholders {}, but the syntax is slightly different:

You can add parameters inside the curly brackets to specify how to convert the value:

Check out all formatting types in our String format() Reference.

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Multiple Values

If you want to use more values, just add more values to the format() method:

And add more placeholders:

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Index Numbers

You can use index numbers (a number inside the curly brackets {0}) to be sure the values are placed in the correct placeholders:

Also, if you want to refer to the same value more than once, use the index number:

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Named Indexes

You can also use named indexes by entering a name inside the curly brackets {carname}, but then you must use names when you pass the parameter values txt.format(carname = "Ford"):

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