CODEWITHSUNDEEP
pythonregex
shweta
shweta

Reputation: 117

Regex Quantifier for exactly one

I have few patterns like:

orange.*
*.key.*
jug.*.key

Here, by * - I mean exactly one word.

So, the pattern *.key.* should match the string bar.key.door (one word on each side) but not fruit.bar.key.door (two words before key).

How do i write a regex pattern for this in Python?

Upvotes: 0

Views: 1170

Answers (3)

The fourth bird
The fourth bird

Reputation: 163497

One way you could match that pattern is to use anchors to assert the start ^ and the end $ of the line and match match the unknown part by using ^[^.]+ (a negated character class) or use \w+ to match one or more word characters.

For example:

^[^.]+\.key\.[^.]+$

import re
p = re.compile('^[^.]+\.key\.[^.]+$')
m = p.match('bar.key.door')
print (m.group())

Demo

Some options for your other patterns could be: ^orange\.\w+$ and ^jug\.[^.]+\.key$

Upvotes: 1

Aman Chhabra
Aman Chhabra

Reputation: 3894

There are various ways to implement it:

Option 1: ^[\w]+\.key\.[\w]+$
Option 2: ^[[:word:]]+\.key\.[[:word:]]+$
Option 3: ^[^.]+\.key\.[^.]+$
Option 4: ^[A-Za-z]+\.key\.[A-Za-z]+$

Hope it helps.

Upvotes: 0

Haleemur Ali
Haleemur Ali

Reputation: 28313

. matches any character except a newline. to match the literal . it needs to be escaped, like \..

* - means exactly 1 word

* is another regex character meaning match 0 or more repetitions of the previous character group. \w+ would match a word. a single word would imply the string terminates (before or after), so it can be checked for using ^ or $.

check out the official re library documentation for more info. It has worked examples and is a very good tutorial for learning regex.

so, the 3 regex patterns would be:

p1 = r'orange\.\w+$'
p2 = r'^\w+\.key\.\w+$'
p3 = r'^jug\.\w+\.key$'

Upvotes: 0

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