Python Regex for Numeric Pattern that has Dashes

Question

I have a column in a pandas data frame called sample_id. Each entry contains a string, from this string I'd like to pull a numeric pattern that will have one of two forms

1-234-5-6789

or

123-4-5648

I'm having trouble defining the correct regex pattern for this. So far I have been experimenting with the following:

re.findall(pattern=r'\b2\w+', string=str(data['sample_id']))

But this is only pulling values that are starting with 2 and only the first chunk of the numeric pattern. How do I express the above patterns with the dashes?

What is your expected output? Do you want only the numbers?

Dani Mesejo
– Dani Mesejo

2018-10-30 17:22:36 +00:00
Commented Oct 30, 2018 at 17:22 — Dani Mesejo
– Dani Mesejo, Commented Oct 30, 2018 at 17:22
Numbers and hyphens would be best.

Sepatau
– Sepatau

2018-10-30 17:26:03 +00:00
Commented Oct 30, 2018 at 17:26 — Sepatau
– Sepatau, Commented Oct 30, 2018 at 17:26
Something like (?<![\d-])(?:\d-)?\d{3}-\d-\d{4}(?![\d-]) ?

user557597
– user557597

2018-10-30 17:41:19 +00:00
Commented Oct 30, 2018 at 17:41 — user557597
– user557597, Commented Oct 30, 2018 at 17:41

Richard · Accepted Answer · 2018-10-30 17:29:49Z

1

A vertical pipe | makes an OR in a regular expression, so you can use:

test1='123-4-5648'
test2='1-234-5-6789'

re.findall(pattern=r'[0-9]-[0-9]{3}-[0-9]-[0-9]{4}|[0-9]{3}-[0-9]-[0-9]{4}', string=test1)
re.findall(pattern=r'[0-9]-[0-9]{3}-[0-9]-[0-9]{4}|[0-9]{3}-[0-9]-[0-9]{4}', string=test2)

[0-9] matches a single digit in the range 0 through 9 (inclusive), {4} indicates that four such digits should occur in a row, - means a hyphen, and | means an OR and separates the two patterns you mention.

answered Oct 30, 2018 at 17:29

Richard

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Comments

The fourth bird · Accepted Answer · 2018-10-31 15:10:59Z

1

You could match an optional part (?:\d-)? to match 1 digit and a hypen, followed by \d{3}-\d-\d{4} which will match the pattern of the digits for both the examples.

(?:\d-)?\d{3}-\d-\d{4}

Regex demo

Instead of using a word boundary \b, if there can not be a non whitespace character before your value, you could prepend the regex with (?<!\S) and if there can not be a non whitespace character after you could add (?!\S) at the end.

edited Oct 31, 2018 at 15:10

answered Oct 30, 2018 at 17:30

The fourth bird

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Comments

Arihant Bansal · Accepted Answer · 2018-10-30 17:25:23Z

0

If there will only a maximum of one hyphen between two numbers then, ^[0-9]+(-[0-9]+)+$ would work well. It uses the normal*(special normal*)* pattern where normal is [0-9] and special is -.

answered Oct 30, 2018 at 17:25

Arihant Bansal

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1 Comment

Richard Over a year ago

This matches 1-1111111-1-1-1-1-1-1-1-1-1-1, which is not one of OP's patterns.

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