[docs] [issue25433] whitespace in strip()/lstrip()/rstrip()

Dimitri Papadopoulos Orfanos report at bugs.python.org
Mon Jan 4 04:42:13 EST 2016


Dimitri Papadopoulos Orfanos added the comment:

In Python 2, as far as I can understand, string.whitespace and str.isspace() are different:
* str.isspace() is built upon the C isspace() function and is therefore locale-dependant. Python heavily relies on isspace() to detect "whitespace" characters.
* string.whitespace is a list of "ASCII whitespace characters" carved in stone. As far as I can see string.whitespace is defined but not used anywhere in Python source code.

See source code:
* Modules/stringobject.c around line 3319:
  [...]
  string_isspace(PyStringObject *self)
  {
  [...]
      e = p + PyString_GET_SIZE(self);
      for (; p < e; p++) {
          if (!isspace(*p))
              return PyBool_FromLong(0);
      }
      return PyBool_FromLong(1);
  [...]
* Lib/string.py near line 23:
  whitespace = ' \t\n\r\v\f'

Functions strip()/lstrip()/rstrip() use str.isspace() and have nothing to do with string.whitespace:

* Modules/stringobject.c around line 1861:
[...]
do_strip(PyStringObject *self, int striptype)
{
[...]
    i = 0;
    if (striptype != RIGHTSTRIP) {
        while (i < len && isspace(Py_CHARMASK(s[i]))) {
            i++;
        }
    }
[...]

Therefore I suggest the documentation of Python 2.7 points to str.isspace() wherever the term "whitespace" is used in the documentation - including this specific case of strip()/lstrip()/rstrip().

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<http://bugs.python.org/issue25433>
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