validationma...@gmail.com wrote:
> i have a code in python to search and replace what i need though is to
> replace the first say 10 instances of the number 1 with 2 and the second
> 10 instances with the number 3. anybody knows how to do that?
>
> fin = open(r'F:\1\xxx.txt')
> fout = open(r'F:\1\xxx2.txt', "wt")
> for line in fin:
> fout.write( line.replace('1', '2') )
> fin.close()
> fout.close()
If the search token can occur more than once in a line you cannot use
str.replace(). Here's a solution without regular expressions. I implemented
the "repeat something" and the "replace token with something different every
time" separately.
$ cat replace_increasing.py
#!/usr/bin/env python3
from itertools import chain, count, repeat
def repeater(values, repeatcount):
"""
>>> list(repeater("abc", 3))
['a', 'a', 'a', 'b', 'b', 'b', 'c', 'c', 'c']
>>> list(repeater(range(3), 2))
[0, 0, 1, 1, 2, 2]
"""
return chain.from_iterable(repeat(value, repeatcount) for value in
values)
def _ran_out_of_values():
if 0:
yield
raise ValueError("ran out of values")
class Replace:
"""
>>> r = Replace("x", "ABCDEFGH")
>>> r("onextwoxthreex")
'oneAtwoBthreeC'
>>> r("no match")
'no match'
>>> r("x at start")
'D at start'
>>> r("somexsomewhere")
'someEsomewhere'
>>> r("xxx")
'FGH'
>>> try: r("x")
... except ValueError as err: print(err)
ran out of values
"""
def __init__(self, token, replace):
self.token = token
self.replaceiter = chain(replace, _ran_out_of_values())
def __call__(self, line):
parts = line.split(self.token)
return "".join(
chain(
(p + q for p, q in zip(parts[:-1], self.replaceiter)),
parts[-1:]
)
)
def main():
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("infile")
parser.add_argument("outfile")
parser.add_argument("token")
parser.add_argument("-r", "--repeat", type=int, default=10)
args = parser.parse_args()
numberstrings = map(str, count(1))
replace = Replace(args.token, repeater(numberstrings, args.repeat))
with open(args.infile) as instream:
with open(args.outfile, "w") as outstream:
outstream.writelines(map(replace, instream))
if __name__ == "__main__":
main()
As an example let's replace the 'a's in the script above with numbers,
repeated three times:
$ ./replace_increasing.py replace_increasing.py tmp.py a -r3
$ head tmp.py
#!/usr/bin/env python3
from itertools import ch1in, count, repe1t
def repe1ter(v2lues, repe2tcount):
"""
>>> list(repe2ter("3bc", 3))
['3', '3', '4', 'b', 'b', 'b', 'c', 'c', 'c']
>>> list(repe4ter(r4nge(3), 2))
[0, 0, 1, 1, 2, 2]
"""
return ch5in.from_iter5ble(repe5t(v6lue, repe6tcount) for v6lue in
v7lues)
def _r7n_out_of_v7lues():
if 0:
yield
r8ise V8lueError("r8n out of v9lues")
$
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