CODEWITHSUNDEEP
pythonexpression
kyo
kyo

Reputation: 63

Python reuse regular expression

I have to match a text.

Ej:

text = 'C:x=-10.25:y=340.1:z=1;'

Where the values after x,y or z accept values matched by: 

-?\d{1,3}(\.\d{1,2})?

How can i reuse that?

Those are the only values that are variables. All others characters must be fixed. I mean, they must be in that exact order.

There is a shorter way to express this?

r'^C:x=-?\d{1,3}(.\d{1,2})?:y=-?\d{1,3}(.\d{1,2})?:z=-?\d{1,3}(.\d{1,2})?;$'

Upvotes: 4

Views: 656

Answers (3)

Hugoagogo
Hugoagogo

Reputation: 1646

Since the regex I put up had a bug I have removed it.

However whenever I need to develop or test a new regex i generally have a play with online tools that allow you to view the results of your regex in real time.

While not specifically python I generally use this one

Upvotes: 0

S.Lott
S.Lott

Reputation: 391952

Folks do this kind of thing sometimes

label_value = r'\w=-?\d{1,3}(\.\d{1,2})?'
line = r'^C:{0}:{0}:{0};$'.format( label_value )
line_pat= re.compile( line )

This is slightly smarter.

label_value = r'(\w)=(-?\d{1,3}(?:\.\d{1,2})?)'
line = r'^C:{0}:{0}:{0};$'.format( label_value )
line_pat= re.compile( line )

Why? It collects the label and the entire floating-point value, not just the digits to the right of the decimal point.

In the unlikely case that order of labels actually does matter.

value = r'(-?\d{1,3}(?:\.\d{1,2})?)'
line = r'^C:x={0}:y={0}:z={0};$'.format( value )
line_pat= re.compile( line )

This requires the three labels in the given order. One of those things that's likely to change.

Upvotes: 8

Aaron Dufour
Aaron Dufour

Reputation: 17525

This will return no false negatives, but a small number of false positives:

'^C(:[xyz]=-?\d{1,3}(.\d{1,2})?){3}'

The false positives are the cases where x, y, and z occur in the wrong combinations (i.e. y:x:z, x:x:z, etc.).

Upvotes: 0

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