Follow-up to #17419

[jbrockmendel]

This moves a few other 3ish line functions from tslib to tslibs.timezones.

One non-trivial function _get_zone is cut/pasted over.

Replaces imports in inference.pyx and period.pyx with imports from tslibs.timezones. In the inference, case, replaces the import of the python version get_timezone with the cython version _get_zone

• closes #xxxx
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[codecov]

Codecov Report

Merging #17497 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #17497      +/-   ##
==========================================
- Coverage   91.15%   91.13%   -0.02%     
==========================================
  Files         163      163              
  Lines       49534    49534              
==========================================
- Hits        45153    45144       -9     
- Misses       4381     4390       +9

Flag	Coverage Δ
#multiple	88.92% <ø> (ø)	⬆️
#single	40.22% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.72% <0%> (-0.1%)	⬇️

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[codecov]

Codecov Report

Merging #17497 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #17497      +/-   ##
==========================================
- Coverage   91.15%   91.13%   -0.02%     
==========================================
  Files         163      163              
  Lines       49534    49534              
==========================================
- Hits        45153    45144       -9     
- Misses       4381     4390       +9

Flag	Coverage Δ
#multiple	88.92% <ø> (ø)	⬆️
#single	40.22% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.72% <0%> (-0.1%)	⬇️

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #17497 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #17497      +/-   ##
==========================================
- Coverage   91.15%   91.13%   -0.02%     
==========================================
  Files         163      163              
  Lines       49534    49534              
==========================================
- Hits        45153    45144       -9     
- Misses       4381     4390       +9

Flag	Coverage Δ
#multiple	88.92% <ø> (ø)	⬆️
#single	40.22% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.72% <0%> (-0.1%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 46856c3...6958c68. Read the comment docs.

[jreback]

looks good
can u run asv (for relevant ones) and report if any issues

[jbrockmendel]

Looks pretty benign:

asv continuous -E virtualenv -f 1.1 master HEAD -b tz -b timezone -b tzone -b utc -b date
       before           after         ratio
     [46856c39]       [6958c680]
+           290ms            407ms     1.40  gil.nogil_read_csv.time_read_csv_datetime
-           16.3s            14.2s     0.87  gil.nogil_datetime_fields.time_datetime_to_period
-           48.3s            41.3s     0.86  gil.nogil_datetime_fields.time_period_to_datetime
-           37.6s            31.6s     0.84  gil.nogil_datetime_fields.time_datetime_field_normalize
-           20.2s            16.3s     0.81  gil.nogil_datetime_fields.time_datetime_field_year
SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.

[jreback]

thanks.

before moving on, can you rename all _* functions in the new modules (tslis/*) to remove the _. These modules themselves are private, not need to have a double layer of indirection.

e.g. _get_zone -> get_zone (actually rename this back to get_timezone), not sure why changed originally.

[jbrockmendel]

Will do.

e.g. _get_zone -> get_zone (actually rename this back to get_timezone), not sure why changed originally.

Maybe this predates the cpdef syntax? get_timezone is currently a regular def function that just passes through to the cdef'd _get_zone.

Speaking of privateness, I've been leaving behind in tslib unused imports from tslibs.foo import _bar # noqa so as to leave the namespace unchanged for backward compat. Are these unnecessary?