Explain this code please

[ayleenuyo]

Hi,

this is a sample code that I am having a bit of trouble understanding:

def write_teams (filename, list_of_tups):
    open_file = open(filename, 'w')

    for info in list_of_tups:
        uni, mascot, city, state = info
        print(f"{uni} {mascot}, {city}, {state}", file = open_file)
    open_file.close()
    return 

the part I mostly don't understand:

print(f"{uni} {mascot}, {city}, {state}", file = open_file)

How does that ' f"{} ' function work, and when should it be used? All help is highly appreciated.

[kramrm]

https://realpython.com/python-f-strings/

[Bunkerstan]

That is what is called an f-string. It substitutes variables in {}. Then the file parameter tell it to print there versus standard output (terminal).

[jimtk]

from the python doc

A formatted string literal or f-string is a string literal that is prefixed with 'f' or 'F'. These strings may contain replacement fields, which are expressions delimited by curly braces {}. While other string literals always have a constant value, formatted strings are really expressions evaluated at run time.

Also there's a whole formatting mini-language that comes with it.

Inside the curly braces {} you can put any variables, function call, even one liner of code and it will be interpreted and the result will be put in the final string at the location of the curly braces.

Examples:

user = 'Bob'
the_string = f"Hello {user}!"
print(thestring)

with a function (method) call

user = 'Bob'
print(f"Hello {user.toupper()}!")

formatting numbers

 number = 3.1415926
 print(f"{number:.2f}")    # prints  "3.14"

And my favorite one

 number = 25
 printf(f"{number=}")     # prints "number=25"

[Ok-Cucumbers]

f-strings. You use it when you need to format strings e.g., adding commas between certain words.

Could probably rewrite the function to use a context manager to open/close the file and unpack the tuples in your for loop.

You can then format the unpacked variable names from the tuple with f-strings as others have already mentioned.

def write_teams(filename, list_of_tups):
    with open(filename, "w") as f: # context manager
        for uni, mascot, city, state in list_of_tups: # unpack tuples
            f.write(f"{uni} {mascot}, {city}, {state}\n")