Question

I have a problem with python regex. The result seems fine on regxe buddy, but fails in python.

Set of data i have to match is a list:

['  101  0.  0.\n',
 '  0.  100.\n',
 '  1.  98.5107805\n',
 '  2.  97.0464459\n',
 '  3.  95.6065328\n', ... ]

I have to get all the numbers starting from second line.
For this i used:

pattern = compile(r'\s*(?P<raw_time>\d*\.?\d*)\s+(?P<raw_value>\d*\.\d*)')

And all worked fine. I iterate through the list and get the first value in “raw_time” and second one in “raw_value” for every line.
Then i was supposed to expand the term to also work with weighted data.

So the data turned to:

['  101  0.  0.\n',
 '  0.  100.  1\n',
 '  1.  98.5107805  1\n',
 '  2.  97.0464459  1\n',
 '  3.  95.6065328  1\n', ... ]

I still just have to parse out two first parameters. So i changed the pattern to:

pattern = compile(r'\s*(?P<raw_time>\d*\.?\d*)\s+(?P<raw_value>\d*\.\d*).+')

It works fine all lines except the 1.

Working:

In [35]: pattern.search('1.  98.5107805  1\n').groupdict()
Out[35]: {'raw_time': '1.', 'raw_value': '98.5107805'}

Working:

In [37]: pattern.search('  0.  100.  1\n').groupdict()
Out[37]: {'raw_time': '0.', 'raw_value': '100.'}

Working:

In [44]: pattern.search(‘1. 98.5107805\n’).groupdict()
Out[44]: {‘raw_time’: ‘1.’, ‘raw_value’: ‘98.510780’}

Not working:

In [46]: pattern.search('  0.  100.\n').groupdict()
Out[46]: {'raw_time': '', 'raw_value': '0.'}

I heavily rely on regex (sure, demo, but it was consistent with python till now).

Advice?

tnx

Answer 1

The .+ that you’ve added needs to be changed to .*.

The + operator requires at least one character, whereas * will accept zero or more.