Python String Formatting

To make sure a string will display as expected, we can format the result with the format() method.

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String format()

The format() method allows you to format selected parts of a string.

Sometimes there are parts of a text that you do not control, maybe they come from a database, or user input?

To control such values, add placeholders (curly brackets {}) in the text, and run the values through the format() method:

Example

Add a placeholder where you want to display the price:

price = 49
txt = "The price is {} dollars"
print(txt.format(price))

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

Example

Format the price to be displayed as a number with two decimals:

txt = "The price is {:.2f} dollars"

Multiple Values

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

print(txt.format(price, itemno, count))

And add more placeholders:

Example

quantity = 3
itemno = 567
price = 49
myorder = "I want {} pieces of item number {} for {:.2f} dollars."
print(myorder.format(quantity, itemno, price))

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:

Example

quantity = 3
itemno = 567
price = 49
myorder = "I want {0} pieces of item number {1} for {2:.2f} dollars."
print(myorder.format(quantity, itemno, price))

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

Example

age = 36
name = "John"
txt = "His name is {1}. {1} is {0} years old."
print(txt.format(age, name))

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"):

Example

myorder = "I have a {carname}, it is a {model}."
print(myorder.format(carname = "Ford", model = "Mustang"))

Python String format() Method

Example

Insert the price inside the placeholder, the price should be in fixed point, two-decimal format:

txt = "For only {price:.2f} dollars!"
print(txt.format(price = 49))

Definition and Usage

The format() method formats the specified value(s) and insert them inside the string's placeholder.

The placeholder is defined using curly brackets: {}. Read more about the placeholders in the Placeholder section below.

The format() method returns the formatted string.

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Syntax

string.format(value1, value2...)

Parameter Values

Parameter	Description
value1, value2...	Required. One or more values that should be formatted and inserted in the string. The values are either a list of values separated by commas, a key=value list, or a combination of both. The values can be of any data type.

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The Placeholders

The placeholders can be identified using named indexes {price}, numbered indexes {0}, or even empty placeholders {}.

Example

Using different placeholder values:

txt1 = "My name is {fname}, I'm {age}".format(fname = "John", age = 36)
txt2 = "My name is {0}, I'm {1}".format("John",36)
txt3 = "My name is {}, I'm {}".format("John",36)

Formatting Types

Inside the placeholders you can add a formatting type to format the result:

:<	Left aligns the result (within the available space)
:>	Right aligns the result (within the available space)
:^	Center aligns the result (within the available space)
:=	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 lower case e
:E	Scientific format, with an upper case 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

#Use "%" to convert the number into a percentage format:

txt = "You scored {:%}"
print(txt.format(0.25))

#Or, without any decimals:

txt = "You scored {:.0%}"
print(txt.format(0.25))

#Use "X" to convert the number into upper-case Hex format:

txt = "The Hexadecimal version of {0} is {0:X}"

print(txt.format(255))

#Use "d" to convert a number, in this case a binary number, into decimal number format:

txt = "We have {:d} chickens."
print(txt.format(0b101))