What does = (equal) do in f-strings inside the expression curly brackets?

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The usage of {} in Python f-strings is well known to execute pieces of code and give the result in string format (some tutorials here). However, what does the '=' at the end of the expression mean?

log_file = open("log_aug_19.txt", "w") 
console_error = '...stuff...'           # the real code generates it with regex

This is actually a brand-new feature as of Python 3.8.

Added an = specifier to f-strings. An f-string such as f'{expr=}' will expand to the text of the expression, an equal sign, then the representation of the evaluated expression.

Essentially, it facilitates the frequent use-case of print-debugging, so, whereas we would normally have to write:


we can now write:


So, as a demonstration, using a shiny-new Python 3.8.0 REPL:

>>> print(f"{foo=}")

PEP 498 -- Literal String Interpolation, Learn about the f-string formatting technique in Python 3.6. The string will be enclosed in single, double, or triple quotes. The variables in the curly { } braces are displayed in the output as a normal print statement. It's very, very exciting to use expressions inside a string. f-string allows us to evaluate� “F-strings provide a way to embed expressions inside string literals, using a minimal syntax. It should be noted that an f-string is really an expression evaluated at run time, not a constant value. In Python source code, an f-string is a literal string, prefixed with f, which contains expressions inside braces. The expressions are replaced

As mention here:

Equals signs are now allowed inside f-strings starting with Python 3.8. This lets you quickly evaluate an expression while outputting the expression that was evaluated. It's very handy for debugging.:

It mean it will run the execution of the code in the f-string braces, and add the result at the end with the equals sign.

So it virtually means:

"something={executed something}"

f-string Formatting in Python, By the end of this article, you will learn how and why to start using f-strings today. At runtime, the expression inside the curly braces is evaluated in its own� This week, we’re looking at curly brackets or braces: {}. Array Builder. You have already encountered curly brackets before in The Meaning of Dot. There, the focus was on the use of the dot/period (.), but using braces to build a sequence was equally important. As we saw then: echo {0..10} prints out the numbers from 0 to 10. Using: echo {10..0}

From Python 3.8, f-strings support "self-documenting expressions", mostly for print de-bugging. From the docs:

Added an = specifier to f-strings. An f-string such as f'{expr=}' will expand to the text of the expression, an equal sign, then the representation of the evaluated expression. For example:

user = 'eric_idle'
member_since = date(1975, 7, 31)
f'{user=} {member_since=}'
"user='eric_idle' member_since=datetime.date(1975, 7, 31)"

The usual f-string format specifiers allow more control over how the result of the expression is displayed:

>>> delta = date.today() - member_since
>>> f'{user=!s}  {delta.days=:,d}'
'user=eric_idle  delta.days=16,075'

The = specifier will display the whole expression so that calculations can be shown:

>>> print(f'{theta=}  {cos(radians(theta))=:.3f}')
theta=30  cos(radians(theta))=0.866

Python 3's f-Strings: An Improved String Formatting Syntax (Guide , An f-string is a specific type of Python string pre-pended with an f that can include variables enclosed Inside the f-string, there is a variable enclosed in curly braces {a} . a = 5 print(f'The f-string says a is equal to {a}') print('The regular string says a is equal to {a}') Expressions like 2+2 can also be placed inside f- strings. Regular expressions (shortened as "regex") are special strings representing a pattern to be matched in a search operation. They are an important tool in a wide variety of computing applications, from programming languages like Java and Perl , to text processing tools like grep , sed , and the text editor vim .

This was introduced in python 3.8. It helps reduce a lot of f'expr = {expr} while writing codes. You can check the docs at What's new in Python 3.8.

A nice example was shown by Raymond Hettinger in his tweet:

>>> from math import radians, sin
>>> for angle in range(360):
        print(f'{angle=}\N{degree sign} {(theta:=radians(angle))=:.3f}')
angle=0° (theta:=radians(angle))=0.000
angle=1° (theta:=radians(angle))=0.017
angle=2° (theta:=radians(angle))=0.035
angle=3° (theta:=radians(angle))=0.052
angle=4° (theta:=radians(angle))=0.070
angle=5° (theta:=radians(angle))=0.087
angle=6° (theta:=radians(angle))=0.105
angle=7° (theta:=radians(angle))=0.122
angle=8° (theta:=radians(angle))=0.140
angle=9° (theta:=radians(angle))=0.157
angle=10° (theta:=radians(angle))=0.175

You can also check out this to get the underlying idea on why this was proposed in the first place.

f-Strings, We can see that the expression a + b within the f-string f{a + b} gets any other python expression) enclosed within the curly braces and then� Brackets are basically symbols which are used in pairs to represent a group composed of various members. There are various types of brackets like - Round or parentheses with symbol Square or box brackets with symbol [] Braces or curly brackets with symbol {} Angle brackets <> However generally, the term brackets are used for square brackets.

A Closer Look At How Python f-strings Work, The parts of the f-string outside of braces are literal strings. Doubled literal opening braces do not signify the start of an expression. Using brackets in python Oct 20, 2013 � Data within literal curly brackets using Python format() & ( verbiage overflow) I'm trying to find issues where the field contents are not equal to {}. You'll come across many symbols in mathematics and arithmetic. In fact, the language of math is written in symbols, with some text inserted as needed for clarification. Three important—and related—symbols you'll see often in math are parentheses, brackets, and braces, which you'll encounter frequently in prealgebra and al

Escape curly braces python, You need to escape curly braces when you are interpolating into a string with . known The contents may be any python expression, which will be escaped according to I'm trying to find issues where the field contents are not equal to {}. f-string is a literal string, prefixed with f, which contains expressions inside braces. The curly brackets (in this case) tell us that you've told Excel to treat the function as an arrayed function. To my understanding, when this is done, Excel knows to designate space in memory for storage of intermediate values when it would not normally do so.

String Formatting with Python 3's f-Strings, F-Strings, are prefixed with an f and contain the replacement fields with curly braces. In this post, we'll look at the various ways we can format strings in Python. include your Python expression inside the string, in between curly brackets. When used in a mathematical expression, left "{" curly brackets, and right "}" curly brackets are used together. They can be interchanged with parenthesis or square brackets.