I have a text file with text that looks like below
Format={ Window_Type="Tabular", Tabular={ Num_row_labels=10 } }
I need to look for Num_row_labels >=10 in my text file. How do I do that using Python 3.2 regex? Thanks.
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Do you need to look for this exact string, or is there any variance?YuriAlbuquerque– YuriAlbuquerque2012-06-26 13:22:55 +00:00Commented Jun 26, 2012 at 13:22
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4 Answers
Assume that the data is formatted as above, and there is no leading 0's in the number:
Num_row_labels=\d{2,}
A more liberal regex which allows arbitrary spaces, still assume no leading 0's:
Num_row_labels\s*=\s*\d{2,}
An even more liberal regex which allows arbitrary spaces, and allow leading 0's:
Num_row_labels\s*=\s*0*[1-9]\d+
If you need to capture the numbers, just surround \d{2,} (in 1st and 2nd regex) or [1-9]\d+ (in 3rd regex) with parentheses () and refers to it in the 1st capture group.
3 Comments
Igor Chubin
In a "liberal case" it will work incorrect, e.g.
Num_row_labels=02
nhahtdh
@IgorChubin: Fixed and tested.
Nemo
Thanks nhahtdh! Your solution works well too. I really appreciate all your time and effort in testing out all possible cases to get the best match. :) You ROCK!
Use:
match = re.search("Num_row_labels=(\d+)", line)
The (\d+) matches at least one decimal digit (0-9) and captures all digits matched as a group (groups are stored in the object returned by re.search and re.match, which I'm assigning to match here). To access the group and compare compare against 10, use:
if int(match.group(1)) >= 10:
print "Num_row_labels is at least 10"
This will allow you to easily change the value of your threshold, unlike the answers that do everything in the regex. Additionally, I believe this is more readable in that it is very obvious that you are comparing a value against 10, rather than matching a nonzero digit in the regex followed by at least one other digit. What the code above does is ask for the 1st group that was matched (match.group(1) returns the string that was matched by \d+), and then, with the call to int(), converts the string to an integer. The integer returned by int() is then compared against 10.
1 Comment
Nemo
Thanks for the answer. I m literaaly overwhelmed by the # of responses to my question. Python is new to me and regex too. I thought of testing yours first. I m guessting that line in your match = re.search("Num_row_labels=(\d+)", line) would be Format={ Window_Type="Tabular", Tabular={ Num_row_labels=10 } }. Correct?
The regex is Num_row_labels=[1-9][0-9]{1}.*
Now you can use the re python module (take a look here) to analyze your text and extract those
2 Comments
Manuel Faux
I would change the
{1} to {1,} to allow numbers higher than 99 and add braces around the numbers to catch them.
DonCallisto
@ManuelFaux : the "1" tells "at least" so this will catch correctly all the numbers. Try it yourself
the re looks like:
Num_row_labels=[0-9]*[1-9][0-9]+
Example of usage:
if re.search('Num_row_labels=[0-9]*[1-9][0-9]+', line):
print line
The regular expression [0-9]*[1-9][0-9]+ means that in the string must be at least
- one digit from 1 to 9 (
[1-9], symbol class[]in regular expressions means that here can be any symbol from the range specified in the brackets); - and at least one digit from 0 to 9 (but it can be more of them) (
[0-9]+, the+sign in regular expression means that the symbol/expression that stand before it can be repeated 1 or more times).
Before these digits can be any other digits ([0-9]*, that means any digit, 0 or more times). When you already have two digits you can have any other digits before — the number would be greater or equal 10 anyway.
3 Comments
Nemo
@igor Chubin, i would like to try your fixed version as well. Please kindly help. Thanks again for your response.
Eric Finn
@Nemo By "fixed", he means that he edited his answer to fix it; what you see is the fixed version.
Nemo
Thanks Igor Chubin for providing explanation as well. It works well too.