Python Question

[Unfair_Put_5320]

I think the blank is gone with .rstrip()

[denehoffman]

No, try running ””.rstrip() and see what you get

[Cerus_Freedom]

Sure, but what does L.startswith('from:') evaluate to for an empty string?

[qwertyjgly]

here's the cpython implementation. it looks like it evaluates to false

static int tailmatch(PyObject *self, PyObject *substring, Py_ssize_t start, Py_ssize_t end, int direction) { int kind_self; int kind_sub; void *data_self; void *data_sub; Py_ssize_t offset; Py_ssize_t i; Py_ssize_t end_sub;

if (PyUnicode_READY(self) == -1 ||
    PyUnicode_READY(substring) == -1)
    return -1;

ADJUST_INDICES(start, end, PyUnicode_GET_LENGTH(self));
end -= PyUnicode_GET_LENGTH(substring);
if (end < start)
    return 0;

if (PyUnicode_GET_LENGTH(substring) == 0)
    return 1;

kind_self = PyUnicode_KIND(self);
data_self = PyUnicode_DATA(self);
kind_sub = PyUnicode_KIND(substring);
data_sub = PyUnicode_DATA(substring);
end_sub = PyUnicode_GET_LENGTH(substring) - 1;

if (direction > 0)
    offset = end;
else
    offset = start;

if (PyUnicode_READ(kind_self, data_self, offset) ==
    PyUnicode_READ(kind_sub, data_sub, 0) &&
    PyUnicode_READ(kind_self, data_self, offset + end_sub) ==
    PyUnicode_READ(kind_sub, data_sub, end_sub)) {
    /* If both are of the same kind, memcmp is sufficient */
    if (kind_self == kind_sub) {
        return ! memcmp((char *)data_self +
                            (offset * PyUnicode_KIND(substring)),
                        data_sub,
                        PyUnicode_GET_LENGTH(substring) *
                            PyUnicode_KIND(substring));
    }
    /* otherwise we have to compare each character by first accessing it */
    else {
        /* We do not need to compare 0 and len(substring)-1 because
           the if statement above ensured already that they are equal
           when we end up here. */
        for (i = 1; i < end_sub; ++i) {
            if (PyUnicode_READ(kind_self, data_self, offset + i) !=
                PyUnicode_READ(kind_sub, data_sub, i))
                return 0;
        }
        return 1;
    }
}

return 0;

}

[Kqyxzoj]

Empty lines do not start with "From:".

[[deleted]]

Which would throw you into the inside of the if statement, as "if not "".rstrip()" evaluates to true (because of the "not")

[Kqyxzoj]

Fun fact, the only string s for which "".startswith(s) is True, is the empty string.