Added const where avaible (#32893)

* Added `const` where avaible

* Trying to use memoryviews

REF:
https://github.com/pandas-dev/pandas/pull/32893/files#r396033598

* Nitpick, added a trailing comma

Co-authored-by: MomIsBestFriend <>

Author: ShaharNaveh

pandas/_libs/tslibs/conversion.pyx

@@ -595,8 +595,12 @@ cdef inline void localize_tso(_TSObject obj, tzinfo tz):
     obj.tzinfo = tz
 
 
-cdef inline bint _infer_tsobject_fold(_TSObject obj, ndarray[int64_t] trans,
-                                      int64_t[:] deltas, int32_t pos):
+cdef inline bint _infer_tsobject_fold(
+    _TSObject obj,
+    const int64_t[:] trans,
+    const int64_t[:] deltas,
+    int32_t pos,
+):
     """
     Infer _TSObject fold property from value by assuming 0 and then setting
     to 1 if necessary.
@@ -738,7 +742,7 @@ def normalize_i8_timestamps(int64_t[:] stamps, object tz):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-cdef int64_t[:] _normalize_local(int64_t[:] stamps, tzinfo tz):
+cdef int64_t[:] _normalize_local(const int64_t[:] stamps, tzinfo tz):
     """
     Normalize each of the (nanosecond) timestamps in the given array by
     rounding down to the beginning of the day (i.e. midnight) for the
@@ -818,7 +822,7 @@ cdef inline int64_t _normalized_stamp(npy_datetimestruct *dts) nogil:
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def is_date_array_normalized(int64_t[:] stamps, object tz=None):
+def is_date_array_normalized(const int64_t[:] stamps, object tz=None):
     """
     Check if all of the given (nanosecond) timestamps are normalized to
     midnight, i.e. hour == minute == second == 0.  If the optional timezone

pandas/_libs/tslibs/offsets.pyx

@@ -609,8 +609,13 @@ cdef inline int month_add_months(npy_datetimestruct dts, int months) nogil:
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def shift_quarters(int64_t[:] dtindex, int quarters,
-                   int q1start_month, object day, int modby=3):
+def shift_quarters(
+    const int64_t[:] dtindex,
+    int quarters,
+    int q1start_month,
+    object day,
+    int modby=3,
+):
     """
     Given an int64 array representing nanosecond timestamps, shift all elements
     by the specified number of quarters using DateOffset semantics.
@@ -759,7 +764,7 @@ def shift_quarters(int64_t[:] dtindex, int quarters,
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def shift_months(int64_t[:] dtindex, int months, object day=None):
+def shift_months(const int64_t[:] dtindex, int months, object day=None):
     """
     Given an int64-based datetime index, shift all elements
     specified number of months using DateOffset semantics

pandas/_libs/tslibs/timedeltas.pyx

@@ -101,7 +101,7 @@ _no_input = object()
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
-def ints_to_pytimedelta(int64_t[:] arr, box=False):
+def ints_to_pytimedelta(const int64_t[:] arr, box=False):
     """
     convert an i8 repr to an ndarray of timedelta or Timedelta (if box ==
     True)

pandas/_libs/tslibs/tzconversion.pyx

@@ -549,8 +549,9 @@ cdef int64_t _tz_convert_tzlocal_fromutc(int64_t val, tzinfo tz, bint *fold):
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
-cdef int64_t[:] _tz_convert_dst(int64_t[:] values, tzinfo tz,
-                                bint to_utc=True):
+cdef int64_t[:] _tz_convert_dst(
+    const int64_t[:] values, tzinfo tz, bint to_utc=True,
+):
     """
     tz_convert for non-UTC non-tzlocal cases where we have to check
     DST transitions pointwise.