Python truncate a long string

Question

info = (data[:75] + '..') if len(data) > 75 else data

Even shorter :

info = data[:75] + (data[75:] and '..')

Even more concise:

data = data[:75]

If it is less than 75 characters there will be no change.

If you are using Python 3.4+, you can use textwrap.shorten from the standard library:

Collapse and truncate the given text to fit in the given width.

First the whitespace in text is collapsed (all whitespace is replaced by single spaces). If the result fits in the width, it is returned. Otherwise, enough words are dropped from the end so that the remaining words plus the placeholder fit within width:

>>> textwrap.shorten("Hello  world!", width=12)
'Hello world!'
>>> textwrap.shorten("Hello  world!", width=11)
'Hello [...]'
>>> textwrap.shorten("Hello world", width=10, placeholder="...")
'Hello...'

For a Django solution (which has not been mentioned in the question):

from django.utils.text import Truncator
value = Truncator(value).chars(75)

Have a look at Truncator's source code to appreciate the problem: https://github.com/django/django/blob/master/django/utils/text.py#L66

Concerning truncation with Django: Django HTML truncation

With regex:

re.sub(r'^(.{75}).*$', '\g<1>...', data)

Long strings are truncated:

>>> data="11111111112222222222333333333344444444445555555555666666666677777777778888888888"
>>> re.sub(r'^(.{75}).*$', '\g<1>...', data)
'111111111122222222223333333333444444444455555555556666666666777777777788888...'

Shorter strings never get truncated:

>>> data="11111111112222222222333333"
>>> re.sub(r'^(.{75}).*$', '\g<1>...', data)
'11111111112222222222333333'

This way, you can also "cut" the middle part of the string, which is nicer in some cases:

re.sub(r'^(.{5}).*(.{5})$', '\g<1>...\g<2>', data)

>>> data="11111111112222222222333333333344444444445555555555666666666677777777778888888888"
>>> re.sub(r'^(.{5}).*(.{5})$', '\g<1>...\g<2>', data)
'11111...88888'

You could use this one-liner:

data = (data[:75] + '..') if len(data) > 75 else data