The f in f-strings may as well stand for “fast.” In this lesson, you’ll see how f-strings are faster than both the %-formatting and str.format()
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F-Strings Speed Considerations & Performance
00:00
What about speed? f-strings are faster than both %-formatting and str.format(). At runtime, each expression inside the curly braces gets evaluated within its own scope, and then it’s put together into the final string.
00:14
Let me have you do a few speed comparisons. For this comparison, you’ll need to import timeit from the standard library, and then create the statement timeit.timeit().
00:29
I’ll have you use triple quotes (""").
00:34
I’ll have you set the age. And for the first one, we’ll use %-formatting, so after building the string, percent (%) then the tuple, ending with the """, and then a number of times, 10,000 times. Okay.
00:55
Well, what would that look like for .format()? It would start the same, with name and age being set up, but for this one, I’ll have you put your curly braces in, .format(name, age).
01:17
End with the """. And run it 10,000 times also. It took substantially longer. How about the newfangled f-strings? Start the same way, name and age.
01:36
And then here, you place name and age inside the curly braces.
01:44 I’ll have you put your repeats in, again 10,000 times. f-strings are faster than both of them.
01:55 Let me have you run this one more time, just to check. As you can see, f-strings come out on top—faster than both. It looks like f-strings are pretty great.
02:06 But there are some details you need to keep in mind when using them. Let’s go into those next.
Perryg on July 24, 2020
0.2042874999997366
I think I need a faster CPU!
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Levi on March 14, 2020
Interestingly enough, on my laptop %s clocked in at 0.005390200007241219 and the f strings at 0.0057520999980624765.