Terry J. Reedy <tjre...@udel.edu> added the comment:
Replacing an expression with a less clear equivalent expression makes no sense
to me. Anyway, having __missing__ return 120 reduces the benchmark miss time
from 1.2-1.3 to .93, making ParseMis always faster than ParseGet and reducing
the penalty for non-ascii chars.
re.sub + str.replace is slower than translate
import re
import timeit
class ParseMap(dict):
def __missing__(self, key): return 120 # ord('x')
trans = ParseMap((i,120) for i in range(128))
trans.update((ord(c), ord('(')) for c in "({[")
trans.update((ord(c), ord(')')) for c in ")}]")
trans.update((ord(c), ord(c)) for c in "\"'\\\n#")
trans_re = re.compile(r'''[^(){}\[]"'\\\n#]+''')
code='\t a([{b}])b"c\'d\n'*1000 # n = 1, 10, 100, 1000
print(timeit.timeit(
'code.translate(trans)',
number=10000, globals = globals()))
print(timeit.timeit(
"code1 = trans_re.sub('x', code)\n"
"code2 = code1.replace('{', '(')\n"
"code3 = code2.replace('}', ')')\n"
"code4 = code3.replace('[', '(')\n"
"code5 = code4.replace(']', '(')\n"
r"code6 = code5.replace('\nx', '\n')",
number=10000, globals = globals()))
n trans re
1 .06 .09
10 .08 .17
100 .28 1.00
1000 2.2 8.9
Multiply by 100 to get microseconds or seconds for 1000000.
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<https://bugs.python.org/issue32940>
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