String concatenation has been optimized since 2.3, so using += should
be fairly fast.
In my first test, I tried concatentating a 4096 byte string 1000 times
in the following code, and the result was indeed very fast (12.352 ms
on my machine).
import time
t = time.time()
mydata = ""
moredata = "A"*4096
for i in range(1000):
mydata += moredata # 12.352 ms
print "%0.3f ms"%(1000*(time.time() - t))
However, I got a different result in my second test, which is
implemented in a class with a feed() method. This test took 4653.522
ms on my machine, which is 350x slower than the previous test!
class StringConcatTest:
def __init__(self):
self.mydata = ""
def feed(self, moredata):
self.mydata += moredata # 4653.522 ms
test = StringConcatTest()
t = time.time()
for i in range(1000):
test.feed(moredata)
print "%0.3f ms"%(1000*(time.time() - t))
Note that I need to do something to mydata INSIDE the loop, so please
don't tell me to append moredata to a list and then use "".join after
the loop.
Why is the second test so much slower?
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