Python .format()

The .format() string function returns a string with values inserted via placeholders.

Python’s built-in string function .format() converts strings by inserting values passed through placeholders.

{} is a placeholder. All the arguments specified in the format method will be replacing the placeholders in the string.

Syntax

string = "{placeholder_1} {placeholder_2}"
string.format(placeholder_1, placeholder_2)

When using multiple placeholder_ values, they are inserted into the string in the order they appear in .format(). Each value in .format() is assigned with an index starting from 0. When the index is called in the placeholder, the corresponding value will be placed in.

Examples

Using empty placeholders {}:

phrase = "I like to eat {}s and {}s."

formatted_phrase = phrase.format("apple", "orange")

print(formatted_phrase)

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The resulting output shows that the string arguments "apple" and "orange" are placed into new_string in the order they appear in .format():

I like to eat apples and oranges.

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The next example features numbered placeholders {0, 1, 2, ..., n}:

phrase_1 = "{0} before the {1}"

phrase_2 = "{1} before the {0}"

print(phrase_1.format("horse", "cart"))

print(phrase_2.format("horse", "cart"))

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The resulting output shows how the numbered placeholders assigned in .format() are zero-indexed:

horse before the cart
cart before the horse

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This example showcases keywords being used as placeholders:

phrase_1 = "I like to eat {food1}s and {food2}s."
new_phrase_1 = phrase_1.format(food1="apple", food2="orange")

phrase_2 = "I like to eat {food2}s and {food1}s."
new_phrase_2 = phrase_2.format(food1="apple", food2="orange")

print(new_phrase_1)
print(new_phrase_2)

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Similar to the previous example, values in .format() can be used with keyword arguments. When the keyword is called in the placeholder, the corresponding value will be placed in:

I like to eat apples and oranges.
I like to eat oranges and apples.

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Codebyte Example

This last example combines both numbered and keyword placeholders in a single .format() statement:

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