How to make string f-string after variable initiazation? [duplicate]

Question

Let's suppose I get some string and set it to variable - it can't be created as f-string:

str1 = 'date time for {val1} and {val2}'

Then variables inside the string initialized:

val1 = 1
val2 = 77

Calling print(str1) will return 'date time for {val1} and {val2}'. But I would like to get 'date time for 1 and 77'

Is there any function to make a string as a F string? So I want to call something make_F(str1) and get f-string

PS I cant use dict {'val1':1, 'val2':77} with .format because don't know which variables will be needed in the string. I just want magic happen with F-string.

Answer 1

You need:

str1 = 'date time for {val1} and {val2}'

val1 = 1
val2 = 77

print(eval(f"f'{str1}'"))

Answer 2

You first need to describe variables as e.g

var1 = None
var2 = None

Then you can use it with f-string like this:

x = f'print {var1} and {var2}'

print(x)

And thats it, you will get the result.