"Dennis Lee Bieber" wrote in message
news:cnk0sdl5a7p17framc5er811p1230mp...@4ax.com...
On Fri, 12 Oct 2018 07:55:58 +0200, "Frank Millman" <fr...@chagford.com>
declaimed the following:
>I have often read that the quickest way to concatenate a number of
>strings
>is to place them in a list and 'join' them -
>
> C:\Users\User>python -m timeit -s "x='a'*500; y='b'*500; z='c'*500"
>''.join([x, y, z])
> 500000 loops, best of 5: 307 nsec per loop
>
>I seem to have found a quicker method, using the new 'f' format
>operator -
>
> C:\Users\User>python -m timeit -s "x='a'*500; y='b'*500; z='c'*500"
>f'{x}{y}{z}'
> 1000000 loops, best of 5: 226 nsec per loop
But your format operator is tied to just a specific number of
substrings.
The list/join algorithm works when the substrings are gathered on an
ad-hoc basis, and the total number of items is unknown.
collect = []
while True:
ln = raw_input("enter a string (empty line to exit)> ").strip()
#yes, Python 2.x
if not ln: break
collect.append(ln)
result = "".join(collect)
That makes sense, thanks.
My use case is that I am building a string from a number of building
blocks - some of them literal strings, some of them string objects.
As Thomas says, I could have just used the '+' operator. In practice I was
building a list and then joining it. It turns out that the 'f' operator is
faster than both of these methods in my particular case.
Frank
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