Python 3.7.4: 're.error: bad escape \s at position 0'
Solution 1
Just try import regex as re
instead of import re
.
Solution 2
Try fiddling with the backslashes to avoid that regex tries to interpret \s
:
spaced_pattern = re.sub(r"\\\s+", "\\\s+", escaped_str)
now
>>> spaced_pattern
'The\\s+quick\\s+brown\\s+fox\\s+jumped'
>>> print(spaced_pattern)
The\s+quick\s+brown\s+fox\s+jumped
But why?
It seems that python tries to interpret \s
like it would interpret r"\n"
instead of leaving it alone like Python normally does. If you do. For example:
re.sub(r"\\\s+", r"\n+", escaped_str)
yields:
The
+quick
+brown
+fox
+jumped
even if \n
was used in a raw string.
The change was introduced in Issue #27030: Unknown escapes consisting of '\'
and ASCII letter in regular expressions now are errors.
The code that does the replacement is in sre_parse.py
(python 3.7):
else:
try:
this = chr(ESCAPES[this][1])
except KeyError:
if c in ASCIILETTERS:
raise s.error('bad escape %s' % this, len(this))
This code looks for what's behind a literal \
and tries to replace it by the proper non-ascii character. Obviously s
is not in ESCAPES
dictionary so the KeyError
exception is triggered, then the message you're getting.
On previous versions it just issued a warning:
import warnings
warnings.warn('bad escape %s' % this,
DeprecationWarning, stacklevel=4)
Looks that we're not alone to suffer from 3.6 to 3.7 upgrade: https://github.com/gi0baro/weppy/issues/227
![Steele Farnsworth](https://i.stack.imgur.com/Onk9n.jpg?s=256&g=1)
Steele Farnsworth
Updated on March 04, 2021Comments
-
Steele Farnsworth over 3 years
My program looks something like this:
import re # Escape the string, in case it happens to have re metacharacters my_str = "The quick brown fox jumped" escaped_str = re.escape(my_str) # "The\\ quick\\ brown\\ fox\\ jumped" # Replace escaped space patterns with a generic white space pattern spaced_pattern = re.sub(r"\\\s+", r"\s+", escaped_str) # Raises error
The error is this:
Traceback (most recent call last): File "<input>", line 1, in <module> File "/home/swfarnsworth/programs/pycharm-2019.2/helpers/pydev/_pydev_bundle/pydev_umd.py", line 197, in runfile pydev_imports.execfile(filename, global_vars, local_vars) # execute the script File "/home/swfarnsworth/programs/pycharm-2019.2/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile exec(compile(contents+"\n", file, 'exec'), glob, loc) File "/home/swfarnsworth/projects/medaCy/medacy/tools/converters/con_to_brat.py", line 255, in <module> content = convert_con_to_brat(full_file_path) File "/home/swfarnsworth/projects/my_file.py", line 191, in convert_con_to_brat start_ind = get_absolute_index(text_lines, d["start_ind"], d["data_item"]) File "/home/swfarnsworth/projects/my_file.py", line 122, in get_absolute_index entity_pattern_spaced = re.sub(r"\\\s+", r"\s+", entity_pattern_escaped) File "/usr/local/lib/python3.7/re.py", line 192, in sub return _compile(pattern, flags).sub(repl, string, count) File "/usr/local/lib/python3.7/re.py", line 309, in _subx template = _compile_repl(template, pattern) File "/usr/local/lib/python3.7/re.py", line 300, in _compile_repl return sre_parse.parse_template(repl, pattern) File "/usr/local/lib/python3.7/sre_parse.py", line 1024, in parse_template raise s.error('bad escape %s' % this, len(this)) re.error: bad escape \s at position 0
I get this error even if I remove the two backslashes before the
'\s+'
or if I make the raw string (r"\\\s+"
) into a regular string. I checked the Python 3.7 documentation, and it appears that\s
is still the escape sequence for white space.