Python String Formatting

Python String Formatting

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

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:

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:

price = 49
txt = "The price is {:.2f} dollars"
print(txt.format(price))

Multiple Values

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

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:

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))

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"):

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

F-Strings

Python 3.6 introduced f-strings, which are a more readable way to format strings. F-strings are prefixed with f or F and use curly braces to insert values:

name = "John"
age = 36
txt = f"My name is {name}, and I am {age}"
print(txt)

F-strings can also include expressions:

price = 59
txt = f"The price is {price * 1.2} dollars"
print(txt)