How to include a dict comprehension in an f-string?

user_11331463 0
Viewed 488

Is there any way to use dict comprehension inside a fstring? THe case is the following:

a = ['a', 'b', 'c', 'd']
list_comprehension = [v for v in a]
my_f_string = f"dict comprehension {v:None for v in a}"

I do not wanna use format interpolation ("{}".format(dict_comprehension)). I want to use the most pythonic way to include that list comprehension inside the fstring to be used for logging data.

f-string string-interpolation python
3 Answers

Yes, of course there is. You simply need to wrap the comprehension in parenthesis ( ), since two consecutive {s are interpreted as a literal "{" string.

a = ['a', 'b', 'c', 'd']
list_comprehension = [v for v in a]

This works:

my_f_string = f"dict comprehension {({v:None for v in a})}"
print(my_f_string)

Output:

dict comprehension {'a': None, 'b': None, 'c': None, 'd': None}

But, this does not work (Stack Overflow's syntax highlighting also helpfully shows that):

my_f_string = f"dict comprehension {{v:None for v in a}}"
print(my_f_string)

Output:

dict comprehension {v:None for v in a}
user_98358720

What you are trying to do can be simply done as

dict_comp = {v:None for v in a}
my_f_string = f"dict comprehension {dict_comp}"

Or if you really want to use a dict comprehension inside an f-string then you have to place {v:None for v in a} inside another curly braces with a space before and after {v:None for v in a}.

my_f_string = f"dict comprehension { {v:None for v in a} }"
user_24558880

In this case I prefer dict.fromkeys:

my_f_string = f"dict comprehension {dict.fromkeys(a)}"

Shorter and much more elegant :)

And now:

print(my_f_string)

Output:

dict comprehension {'a': None, 'b': None, 'c': None, 'd': None}
user_87083640
Related