How does one truncate a string to 75 characters in Python?
This is how it is done in JavaScript:
var data="saddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsaddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsadddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd"
var info = (data.length > 75) ? data.substring[0,75] + '..' : data;
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 can't actually "truncate" a Python string like you can do a dynamically allocated C string. Strings in Python are immutable. What you can do is slice a string as described in other answers, yielding a new string containing only the characters defined by the slice offsets and step. In some (non-practical) cases this can be a little annoying, such as when you choose Python as your interview language and the interviewer asks you to remove duplicate characters from a string in-place. Doh.
There's no need for a regular expression but you do want to use string formatting rather than the string concatenation in the accepted answer.
This is probably the most canonical, Pythonic way to truncate the string data at 75 characters.
>>> data = "saddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsaddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddsadddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd"
>>> info = "{}..".format(data[:75]) if len(data) > 75 else data
>>> info
'111111111122222222223333333333444444444455555555556666666666777777777788888...'
Here's a function I made as part of a new String class... It allows adding a suffix ( if the string is size after trimming and adding it is long enough - although you don't need to force the absolute size )
I was in the process of changing a few things around so there are some useless logic costs ( if _truncate ... for instance ) where it is no longer necessary and there is a return at the top...
But, it is still a good function for truncating data...
##
## Truncate characters of a string after _len'nth char, if necessary... If _len is less than 0, don't truncate anything... Note: If you attach a suffix, and you enable absolute max length then the suffix length is subtracted from max length... Note: If the suffix length is longer than the output then no suffix is used...
##
## Usage: Where _text = 'Testing', _width = 4
## _data = String.Truncate( _text, _width ) == Test
## _data = String.Truncate( _text, _width, '..', True ) == Te..
##
## Equivalent Alternates: Where _text = 'Testing', _width = 4
## _data = String.SubStr( _text, 0, _width ) == Test
## _data = _text[ : _width ] == Test
## _data = ( _text )[ : _width ] == Test
##
def Truncate( _text, _max_len = -1, _suffix = False, _absolute_max_len = True ):
## Length of the string we are considering for truncation
_len = len( _text )
## Whether or not we have to truncate
_truncate = ( False, True )[ _len > _max_len ]
## Note: If we don't need to truncate, there's no point in proceeding...
if ( not _truncate ):
return _text
## The suffix in string form
_suffix_str = ( '', str( _suffix ) )[ _truncate and _suffix != False ]
## The suffix length
_len_suffix = len( _suffix_str )
## Whether or not we add the suffix
_add_suffix = ( False, True )[ _truncate and _suffix != False and _max_len > _len_suffix ]
## Suffix Offset
_suffix_offset = _max_len - _len_suffix
_suffix_offset = ( _max_len, _suffix_offset )[ _add_suffix and _absolute_max_len != False and _suffix_offset > 0 ]
## The truncate point.... If not necessary, then length of string.. If necessary then the max length with or without subtracting the suffix length... Note: It may be easier ( less logic cost ) to simply add the suffix to the calculated point, then truncate - if point is negative then the suffix will be destroyed anyway.
## If we don't need to truncate, then the length is the length of the string.. If we do need to truncate, then the length depends on whether we add the suffix and offset the length of the suffix or not...
_len_truncate = ( _len, _max_len )[ _truncate ]
_len_truncate = ( _len_truncate, _max_len )[ _len_truncate <= _max_len ]
## If we add the suffix, add it... Suffix won't be added if the suffix is the same length as the text being output...
if ( _add_suffix ):
_text = _text[ 0 : _suffix_offset ] + _suffix_str + _text[ _suffix_offset: ]
## Return the text after truncating...
return _text[ : _len_truncate ]
Simple and short helper function:
def truncate_string(value, max_length=255, suffix='...'):
string_value = str(value)
string_truncated = string_value[:min(len(string_value), (max_length - len(suffix)))]
suffix = (suffix if len(string_value) > max_length else '')
return string_truncated+suffix
Usage examples:
# Example 1 (default):
long_string = ""
for number in range(1, 1000):
long_string += str(number) + ','
result = truncate_string(long_string)
print(result)
# Example 2 (custom length):
short_string = 'Hello world'
result = truncate_string(short_string, 8)
print(result) # > Hello...
# Example 3 (not truncated):
short_string = 'Hello world'
result = truncate_string(short_string)
print(result) # > Hello world
