What does 'f' means before a string in Python?

Question

I\'m new here and also new to Python. I wonder what does f in print(f\'Column names are {\"-\".join(row)}\') do I tried deleting it and then \'Column n

Answer 1

This is called f-strings and are quite straightforward : when using an "f" in front of a string, all the variables inside curly brackets are read and replaced by there value. For example :

    age = 18
    message = f"You are {age} years old"
    print(message)

Will return "You are 18 years old"

This is similar to str.format (https://docs.python.org/3/library/stdtypes.html#str.format) but in a more concise way.

Answer 2

String starting with f are formatted string litrals.

Suppose you have a variable:

pi = 3.14

To catenate it to a string you'd do:

s = "pi = " + str(pi)

Formatted strings come in handy here. Using them you can use this do the same:

s = f"pi = {pi}"

{pi} is simply replaced by the value in the pi

Answer 3

join method returns a string in which the elements of sequence have been joined by a separator. In your code, it takes row list and join then by separator -.

Then by using f-string, expression specified by {} will be replaced with it's value.

Suppose that row = ["1", "2", "3"] then output will be Column names are 1-2-3.