How to use f-strings in Python | note.nkmk.me (2024)

FAQs

How do you do F-strings in Python? ›

To use formatted string literals, begin a string with f or F before the opening quotation mark or triple quotation mark. Inside this string, you can write a Python expression between { and } characters that can refer to variables or literal values.

Using f-strings, your code will not only be cleaner but also faster to write. With f-strings you are not only able to format strings but also print identifiers along with a value (a feature that was introduced in Python 3.8).

In Python source code, an f-string is a literal string, prefixed with 'f', which contains expressions inside braces. The expressions are replaced with their values. Some examples are: >>> import datetime >>> name = 'Fred' >>> age = 50 >>> anniversary = datetime.

The format specifier . 2f states that we want to display 2 decimals. The letter f at the end means that we want the variable to be displayed as a float , i.e. a floating point number. You can think of an f-string as a sort of function, which creates a normal string based on the "arguments" within the curly brackets.

Python 3.6+ has introduced f-strings support in which keys of a dictionary can be used to format a string. In this approach, you need to place the f prefix before the string and place the key of the dictionary inside the curly braces { }.

We can use any quotation marks {single or double or triple} in the f-string. We have to use the escape character to print quotation marks. The f-string expression doesn't allow us to use the backslash. We have to place it outside the { }.

Python has several tools for string interpolation that support many formatting features. In modern Python, you'll use f-strings or the .format() method most of the time. However, you'll see the modulo operator ( % ) being used in legacy code.

Conciseness: F-strings provide a concise syntax for string formatting, reducing the amount of code required compared to other methods.

Python f-strings or formatted strings are the new way to format strings. This feature was introduced in Python 3.6 under PEP-498.

Can you use F-strings in logging Python? ›

Using f-strings to format a logging message requires that Python eagerly format the string, even if the logging statement is never executed (e.g., if the log level is above the level of the logging statement), whereas using the extra keyword argument defers formatting until required.

Rounding Numbers With F-Strings

F-strings can also be used to round numbers to a specific precision, using the round() function. To round a number using f-strings, simply include the number inside the curly braces, followed by a colon and the number of decimal places to round to.

Explanation: format() method is called on the float value, specifying '{:.2f}' as the format specifier. {:.2f} format specifier indicates that the float should be formatted with two decimal places. The formatted value is stored in formatted_value. Finally, print() function is used to display the formatted value.

%f is for floats. 02:01 In addition to the indicator, you can also put formatting information. The 0.2 here tells Python to put as many digits to the left of the decimal as you like, but only 2 significant digits to the right. 02:15 This formatting will work in more than just floats.

For instance, if we want to display a floating-point number with one decimal place, we can use :. 1f inside the braces and after the expression.

Concatenating Strings in Python Using f-Strings

Python f-strings are prefixed by the letter f and allow you to place variables to interpolate into square brackets. The variables are evaluated at run-time, and their string representation is placed into the string. print(f'Welcome to {website}!' )

Using Backslashes

The backslashes tell Python to ignore the newline characters in the code and join the f-strings into one single line. Using backslashes, you can create multiline strings with f-strings without having to use triple quotes or escape characters. This can make your code more compact and efficient.

Assigning a string in Python is done by enclosing the text within either single quotes (' '), double quotes (" "), or triple quotes (''' ''' or """ """).