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Python Python Sequences Sequence Iteration Iterating with Enumerate

Printing template literals in python "{item}" vs. "{}.format(item)"

Is there a reason why/helpful way to remember which format literal is used where? In most of the places I've learned so far, it works like this:

bugs = ["ants", "bees", "squash bugs", "chiggers"]
for e in bugs:
    print("There are so many {} outside!".format(e))

But, for f-string, it only works like this:

bugs = ["ants", "bees", "squash bugs", "chiggers"]
print("Bugs outside:")
for index, e in enumerate(bugs, 1):
    print(f'{index}. {e}')

I'm guessing there is a reason for this, but the switch from the .format method to putting the variables inside the curly braces isn't obvious to me. Thanks!

2 Answers

Chris Freeman
Chris Freeman
Treehouse Moderator 67,736 Points

Hey amandae, There are many ways to format a string in Python.

The f-strings, formatted string literals, is the latest addition, first appearing in Python 3.6.

The more complex (and flexible) previous method is using the str.format() method. This is is still widely used, and has additional features (like repeatable, reorderable fields) so expect it to stick around for a long time.

With the format method, the {} placeholders can taking on many forms:

  • as order-dependent placeholders when empty: "{} before {}".format(first, last)
  • as indexed-dependent placeholders when numbered: "{1} before {0}".format(goes2zero, goes2one)`
  • as named placeholders: "{first} before {last}".format(first=goes2first, last=goes2last)`

So, about remembering the difference. The "f" in front of f-strings can be thought of as fancy, where it is a shortcut to the named placeholder version of format without having to add the .format(first=first, last=last) method. The "f" can also be thought of as fast, since f-stings have been optimized to be the fasted string handling in python!!

Post back if you need more help. Good luck!!

Thank you so much! Your answer is wonderfully helpful!