Both ternaries ("if expressions") and comprehensions ("for expressions") are allowed inside f-strings. However, they must be part of expressions that evaluate to strings. For example, key: value is a dict pair, and f"{key}: {value}" is required to produce a string.
>>> dct = {'a': 1, 'b': 2}
>>> newline = "\n" # \escapes are not allowed inside f-strings
>>> print(f'{newline.join(f"{key}: {value}" for key, value in dct.items())}')
a: 1
b: 2
Note that if the entire f-string is a single format expression, it is simpler to just evaluate the expression directly.
>>> print("\n".join(f"{key}: {value}" for key, value in dct.items())))
a: 1
b: 2
Expressions inside format strings still follow their regular semantics. For example, a ternary may test whether an existing name is true. It will fail if the name is not defined.
>>> c, name = "Hello", ""
>>> f'{c} {name if name else "unknown"}'
'Hello unknown'
>>> del name
>>> f'{c} {name if name else "unknown"}'
NameError: name 'name' is not defined
Python for Network Engineers
pyneng.readthedocs.io › en › latest › book › 08_python_basic_examples › f-string.html
Formatting lines with f-strings - Python for network engineers
When using f-strings in loops an f-string must be written in body of the loop to «catch» new variable values within each iteration:
using f-string's with a list
Did you try names = [‘Adam’, ‘Bob’, ‘Cyril] text = f”””Winners are : {names}. This is print the second name {names[1]} “”” More on reddit.com
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May 3, 2023Why do people use .format() method when f string literal exists?
f-strings exist for convenience. In doing so, they sacrifice portability, flexibility, and functionality. They are not back-wards compatible with python3.5, which is still floating around out there. They also have some drawbacks, like with the normal format method, you can re-use values, e.g. '{0}, {0}, and {1}'.format('ham', 'spam') Can't do that with f-strings. you can also build dynamically formatted strings: a = range(5) ( '{}'*len(a) ).format(*a) Which can be quite complex. there are probably more reasons others will comment about, but in general, f-strings are just for hard-coded generic messages that aren't anything special. the format function is still very necessary. More on reddit.com
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July 1, 2020f-string concatenating string variable outside for loop?
Because the f-string starts with {route}. By doing route = f"{route}{key} {value}
", you're replacing the value of route by a new string that starts with the current value of route. More on reddit.com
", you're replacing the value of route by a new string that starts with the current value of route. More on reddit.com
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December 1, 2022Purpose of the F-string
It's a better alternative if you need to inject several variables into the string, like if you wanted to write: print(f’Movie ticket price: {movie_ticket_price}\n Movie time: {movie_time}\n Movie length: {movie_length}. Etc.’) Is imho easier to read and modify than this, where you need to open and close quotes at every string segment: print(`Movie ticket price:` + movie_ticket_price + `\nMovie time:` + movie_time + `\nMovie length:` + movie_length + `. Etc.’) And those 2 are still, imo, easier to read than % and .format() xD More on reddit.com
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February 23, 2023Videos
Python f-Strings - Advanced String Formatting tutorial for beginners ...
40:38
Python Tutorial (2021) | Learning with Example | f-strings, for-loop ...
String Interpolation with f-Strings in Modern Python an ...
17:00
Python F Strings Explained in 15 Minutes - YouTube
10:51
for Loop with Strings in Python - YouTube
11:16
Python F-Strings: Advanced Tips and Tricks - YouTube
DataCamp
datacamp.com › tutorial › python-f-string
Python f-string: A Complete Guide | DataCamp
December 3, 2024 - When dealing with loops, proper f-string usage becomes particularly important. Here's a comparison of different approaches: # Loop performance comparison data = [("Alice", 95), ("Bob", 87), ("Charlie", 92)] # Less efficient approach - creating new format string each time def format_inefficient(): result = [] for name, score in data: result.append("Name: {} | Score: {}".format(name, score)) return "\n".join(result) # More efficient approach - create template once def format_efficient(): template = "Name: {} | Score: {}" result = [] for name, score in data: result.append(template.format(name, sc
Real Python
realpython.com › python-f-strings
Python's F-String for String Interpolation and Formatting – Real Python
November 30, 2024 - The timeit.timeit() function inside the for loop runs each interpolation tool a million times and returns the total execution time. Then, the function prints the result to the screen. Note how your f-string in the call to print() takes advantage of format specifiers to conveniently format the code’s output.
Sololearn
sololearn.com › en › Discuss › 1612771 › how-to-use-for-loop-inside-f-string
How to use for loop inside f-string? | Sololearn: Learn to code for FREE!
#take this case : names = ['Bob', 'Alice', 'Guido'] for index,value in enumerate(names): print(f"{index}:{value}")
GeeksforGeeks
geeksforgeeks.org › formatted-string-literals-f-strings-python
f-strings in Python - GeeksforGeeks
June 19, 2024 - Let's consider an example to understand it better, suppose you want to change the value of the string every time you print the string like you want to print "hello <name> welcome to geeks for ... In Python, a string of required formatting can be achieved by different methods. Some of them are; 1) Using % 2) Using {} 3) Using Template Strings In this article the formatting using % is discussed. The formatting using % is similar to that of 'printf' in C programming language. %d - integer %f -
W3Schools
w3schools.com › python › python_string_formatting.asp
Python String Formatting
To format values in an f-string, add placeholders {}, a placeholder can contain variables, operations, functions, and modifiers to format the value. ... A placeholder can also include a modifier to format the value.
OpenPython
openpython.org › home › articles › python f-strings and string formatting: the complete guide
Python f-strings and String Formatting: The Complete Guide | OpenPython
3 weeks ago - For large-scale formatting inside tight loops, measure using the timeit module. Q: Can I use assignment expressions (walrus operator) inside f-strings? A: Yes, in Python 3.8+ you can use the walrus operator := inside f-strings, but it must appear in an expression context (often within parentheses for readability).
The Python Coding Stack
thepythoncodingstack.com › the python coding stack › i want my own fancy f-string format specifiers… sure you can
I Want My Own Fancy F-String Format Specifiers… Sure You Can
March 19, 2025 - You then iterate through the format_spec string starting from index f_index + 1. This is the character immediately after the "f". You add each character that isn't a digit or * to sep.
Codecademy Forums
discuss.codecademy.com › t › how-to-use-for-loop-with-string-format-method › 607315
How to use for loop with string format method - Python
August 19, 2021 - Community discussion forums for Codecademy
GitHub
gist.github.com › AlanSimpsonMe › a8c1fbd0e6d45d014d466d62af18d0c9
Loop through nested Python 3.7 dictionaries and format output with f-strings. · GitHub
Loop through nested Python 3.7 dictionaries and format output with f-strings. - Python_3.7_nested_dictionaries_f-strings
Bentley
cissandbox.bentley.edu › sandbox › wp-content › uploads › 2022-02-10-Documentation-on-f-strings-Updated.pdf pdf
A Guide to Formatting with f-strings in Python - CIS Sandbox
When variable = math.pi, the f-string · understands that variable is a floating-point number and displays it as such. You can also · use specify the type as f and use spacing in the output. The following are examples of the exponent notation and the percentage notation: ... There are several options when formatting floating point numbers. The number of decimal · places, the use of the number separator character, and forcing a plus (+) or minus (-) sign can
Medium
pravash-techie.medium.com › python-going-beyond-basic-string-formatting-using-f-string-cba87ddb78fb
Python: Going Beyond Basic String Formatting using f-string | by Pravash | Medium | Medium
March 23, 2023 - An f-string is a string literal that is prefixed with the letter “f”. It allows developers to embed expressions inside string literals, using curly braces {}. These expressions are evaluated at runtime and the resulting values are inserted ...
freeCodeCamp
freecodecamp.org › news › python-f-strings-tutorial-how-to-use-f-strings-for-string-formatting
Python f-String Tutorial – String Formatting in Python Explained with Code Examples
September 14, 2021 - When you're formatting strings in Python, you're probably used to using the format() method. But in Python 3.6 and later, you can use f-Strings instead. f-Strings, also called formatted string literals, have a more succinct syntax and can be super h...
ZetCode
zetcode.com › python › fstring
Python f-string - formatting strings in Python with f-string
May 11, 2025 - Any valid Python expression can be placed within the curly braces, allowing you to perform calculations or manipulate data inline as you format your output. ... #!/usr/bin/python bags = 3 apples_in_bag = 12 print(f'There are total of {bags * apples_in_bag} apples') Here, the expression bags * apples_in_bag is evaluated inside the f-string, and its result is inserted into the output. This makes f-strings very flexible for dynamic string construction.
Reddit
reddit.com › r/learnpython › using f-string's with a list
r/learnpython on Reddit: using f-string's with a list
May 3, 2023 -
just thought id make a post incase anyone has an issue using f-string with a list. i moved on from using .format() to using f-string. i have found it pretty easy to get adjusted to but i was struggling with using specific values within a list, i treid a few methods like:
names = ['Adam', 'Bob', 'Cyril']
text = f'Winners are: {0} {1} {2}'(*names)
print(text)
names = ['Adam', 'Bob', 'Cyril']
text = f'Winners are: {*0} {*1} {*2}'(names)
print(text)
names = ['Adam', 'Bob', 'Cyril']
text = f'Winners are: {[0]} {[1]} {[2]}'(names)
print(text)
all came back with errors and left me stuck on how to use f-string with a list until i watched Corey Schafers video, within the half an hour i was pretty much trying to brute force it, reaching the same error, i found out the correct way of interlopoing a list with a f-string is:
names = ['Adam', 'Bob', 'Cyril']
text = f'Winners are: {names[0]}, {names[1]}, {names[2]}'
print(text)
just thought id make the post incase anyone else is unsure on how.
Top answer 1 of 3
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Did you try names = [‘Adam’, ‘Bob’, ‘Cyril] text = f”””Winners are : {names}. This is print the second name {names[1]} “””
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names = ['Adam', 'Bob', 'Cyril'] text = f'Winners are: {0} {1} {2}'(*names) print(text) names = ['Adam', 'Bob', 'Cyril'] text = f'Winners are: {names[0]}, {names[1]}, {names[2]}' print(text) I don't think you need to go out of your way to use an f-string instead of str.format everywhere. For something like this, names = ['Adam', 'Bob', 'Cyril'] text = "Winners are: {} {} {}".format(*names) print(text) is perfectly fine. But if you insist, I'd suggest str.join: names = ['Adam', 'Bob', 'Cyril'] text = f"Winners are: {', '.join(names)}" print(text) F-strings are great, but they're not always the best option.
datagy
datagy.io › home › python posts › python f-strings: everything you need to know!
Python f-strings: Everything you need to know! • datagy
December 20, 2022 - Learn how to use Python f-strings including using conditions, formatting values, aligning values, and debugging. A video tutorial is included!
Reddit
reddit.com › r/learnpython › why do people use .format() method when f string literal exists?
r/learnpython on Reddit: Why do people use .format() method when f string literal exists?
July 1, 2020 -
Hello all,
I seem to encounter a lot of documentation and tutorials that use .format() method instead of f string literals.
Personally,
print("I can't seem to {} of a {} why someone {} {} {}".format('think', 'reason', 'would', 'prefer', 'this'))versus
easily = "easily"
sentence = "sentence"
this = "this"
print(f"A much more {easily} readable {sentence} such as {this}")F string literal is always much easier to decipher and thus avoid errors.
Perhaps there's some benefit of .format() that I'm unaware of. Googling hasn't brought up much on the debate.
Cheers!
Top answer 1 of 28
212
f-strings exist for convenience. In doing so, they sacrifice portability, flexibility, and functionality. They are not back-wards compatible with python3.5, which is still floating around out there. They also have some drawbacks, like with the normal format method, you can re-use values, e.g. '{0}, {0}, and {1}'.format('ham', 'spam') Can't do that with f-strings. you can also build dynamically formatted strings: a = range(5) ( '{}'*len(a) ).format(*a) Which can be quite complex. there are probably more reasons others will comment about, but in general, f-strings are just for hard-coded generic messages that aren't anything special. the format function is still very necessary.
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f-strings were only introduced in Python 3.6; it's basically nobody's job to go back and update documentation when it still works.
W3Schools
w3schools.com › python › python_strings_format.asp
Python - Format Strings
Python Examples Python Compiler Python Exercises Python Quiz Python Challenges Python Practice Problems Python Server Python Syllabus Python Study Plan Python Interview Q&A Python Bootcamp Python Training ... age = 36 #This will produce an error: txt = "My name is John, I am " + age print(txt) Try it Yourself » · But we can combine strings and numbers by using f-strings or the format() method!
Python Tutorial
pythontutorial.net › home › python basics › python f-strings
Python F-strings: a Practical Guide to F-strings in Python
March 30, 2025 - ... How it works. First, define a variable with the value 'John'. Then, place the name variable inside the curly braces {} in the literal string. Note that you need to prefix the string with the letter f to indicate that it is an f-string. It’s also valid if you use the letter in uppercase ...