def _get_period_alias(freq) -> Optional[str]:
if isinstance(freq, DateOffset):
freq = freq.rule_code
else:
freq = base_and_stride(freq)[0]
freq = get_period_alias(freq)
return freq
def to_offset(freq) -> Optional[DateOffset]:
"""
Return DateOffset object from string or tuple representation
or datetime.timedelta object.
Parameters
----------
freq : str, tuple, datetime.timedelta, DateOffset or None
Returns
-------
DateOffset
None if freq is None.
Raises
------
ValueError
If freq is an invalid frequency
See Also
--------
DateOffset : Standard kind of date increment used for a date range.
Examples
--------
>>> to_offset("5min")
<5 * Minutes>
>>> to_offset("1D1H")
<25 * Hours>
>>> to_offset(("W", 2))
<2 * Weeks: weekday=6>
>>> to_offset((2, "B"))
<2 * BusinessDays>
>>> to_offset(pd.Timedelta(days=1))
<Day>
>>> to_offset(Hour())
<Hour>
"""
if freq is None:
return None
if isinstance(freq, DateOffset):
return freq
if isinstance(freq, tuple):
name = freq[0]
stride = freq[1]
if isinstance(stride, str):
name, stride = stride, name
name, _ = libfreqs.base_and_stride(name)
delta = _get_offset(name) * stride
elif isinstance(freq, timedelta):
delta = None
freq = Timedelta(freq)
try:
for name in freq.components._fields:
offset = _name_to_offset_map[name]
stride = getattr(freq.components, name)
if stride != 0:
offset = stride * offset
if delta is None:
delta = offset
else:
delta = delta + offset
except ValueError as err:
raise ValueError(libfreqs.INVALID_FREQ_ERR_MSG.format(freq)) from err
else:
delta = None
stride_sign = None
try:
split = re.split(libfreqs.opattern, freq)
if split[-1] != "" and not split[-1].isspace():
# the last element must be blank
raise ValueError("last element must be blank")
for sep, stride, name in zip(split[0::4], split[1::4], split[2::4]):
if sep != "" and not sep.isspace():
raise ValueError("separator must be spaces")
prefix = libfreqs._lite_rule_alias.get(name) or name
if stride_sign is None:
stride_sign = -1 if stride.startswith("-") else 1
if not stride:
stride = 1
if prefix in Resolution.reso_str_bump_map:
stride, name = Resolution.get_stride_from_decimal(
float(stride), prefix
)
stride = int(stride)
offset = _get_offset(name)
offset = offset * int(np.fabs(stride) * stride_sign) # type: ignore
if delta is None:
delta = offset
else:
delta = delta + offset
except (ValueError, TypeError) as err:
raise ValueError(libfreqs.INVALID_FREQ_ERR_MSG.format(freq)) from err
if delta is None:
raise ValueError(libfreqs.INVALID_FREQ_ERR_MSG.format(freq))
return delta
