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Creating a dictionary from successful regular expression matches in python

I am new to Python and I am trying to parse a file. Only some lines in the file contain data of interest, and I want to finish using a dictionary of material analyzed from valid matching lines in the file.

The code below works, but it's a little ugly, and I'm trying to find out how this should be done, perhaps with understanding, or with multi-line regex. I am using Python 3.2.

file_data = open('x:\\path\\to\\file','r').readlines()
my_list = []
for line in file_data:
    # discard lines which don't match at all
    if re.search(pattern, line):
        # icky, repeating search!!
        one_tuple = re.search(pattern, line).group(3,2)
        my_list.append(one_tuple)
my_dict = dict(my_list)

Can you suggest a better implementation?

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5 answers

Thanks for answers. Putting them together, I got

file_data = open('x:\\path\\to\\file','r').read()
my_list = re.findall(pattern, file_data, re.MULTILINE)
my_dict = {c:b for a,b,c in my_list}

but I don’t think I could get there today without help.

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:

my_dict = dict()

with open(r'x:\path\to\file', 'r') as data:
    for line in data:
        match = re.search(pattern, line)
        if match:
            one_tuple = match.group(3, 2)
            my_dict[one_tuple[0]] = one_tuple[1]
+4

EAFP

with open(r'x:\path\to\file', 'r') as data:
    for line in data:
        try:
            m = re.search(pattern, line)
            my_dict[m.group(2)] = m.group(3)
        except AttributeError:
            pass

- , , (key, value). :

  matches = [re.findall(pattern, line) for line in data]
  mydict = dict(x[0] for x in matches if x)
+2

I'm not sure I recommend it, but here you can try to use understanding (I just replaced the line for the file)

>>> import re
>>> data = """1foo bar
... 2bing baz
... 3spam eggs
... nomatch
... """
>>> pattern = r"(.)(\w+)\s(\w+)"
>>> {x[0]: x[1] for x in (m.group(3, 2) for m in (re.search(pattern, line) for line in data.splitlines()) if m)}
{'baz': 'bing', 'eggs': 'spam', 'bar': 'foo'}
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matchRes = pattern.match(line)
if matchRes:
    my_dict = matchRes.groupdict()
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