RM-48 factor to_pandas_dtype into dictionary

metrics/flake8_high_water_mark

@@ -1 +1 @@
-5
+4

records_mover/records/schema/field/__init__.py

@@ -199,96 +199,104 @@ def components_to_time_str(df: pd.DataFrame) -> datetime.time:
                      target_type)
         return series.astype(target_type)
 
-    def to_pandas_dtype(self) -> 'Dtype':
+    def process_integer_field_type_to_pd_dtype(self) -> 'Dtype':
         import numpy as np
         import pandas as pd
-        from .pandas import supports_nullable_ints, integer_type_for_range
+        from .pandas import integer_type_for_range, supports_nullable_ints
 
         has_extension_types = supports_nullable_ints()
+        int_constraints =\
+            cast(Optional[RecordsSchemaFieldIntegerConstraints], self.constraints)
+        min_: Optional[int] = None
+        max_: Optional[int] = None
+        required = False
+        if int_constraints:
+            min_ = int_constraints.min_
+            max_ = int_constraints.max_
+            required = int_constraints.required
+
+        if not required and not has_extension_types:
+            logger.warning(f"Dataframe field {self.name} is nullable, but using pandas "
+                           f"{pd.__version__} which does not support nullable integer type")
+
+        if min_ is not None and max_ is not None:
+            dtype = integer_type_for_range(min_, max_, has_extension_types)
+            if dtype:
+                return dtype
+            else:
+                logger.warning("Asked for a type larger than int64 in dataframe "
+                               f"field '{self.name}' - providing float128, but "
+                               "loss of precision will occur!  "
+                               f"Requested min/max values: {min_}/{max_}")
+                return np.float128
+        else:
+            logger.warning(f"No integer constraints provided for field '{self.name}'; "
+                           "using int64")
+            if has_extension_types:
+                return pd.Int64Dtype()
+            else:
+                return np.int64
 
-        if self.field_type == 'integer':
-            int_constraints =\
-                cast(Optional[RecordsSchemaFieldIntegerConstraints], self.constraints)
-            min_: Optional[int] = None
-            max_: Optional[int] = None
-            required = False
-            if int_constraints:
-                min_ = int_constraints.min_
-                max_ = int_constraints.max_
-                required = int_constraints.required
-
-            if not required and not has_extension_types:
-                logger.warning(f"Dataframe field {self.name} is nullable, but using pandas "
-                               f"{pd.__version__} which does not support nullable integer type")
-
-            if min_ is not None and max_ is not None:
-                dtype = integer_type_for_range(min_, max_, has_extension_types)
-                if dtype:
-                    return dtype
-                else:
-                    logger.warning("Asked for a type larger than int64 in dataframe "
-                                   f"field '{self.name}' - providing float128, but "
-                                   "loss of precision will occur!  "
-                                   f"Requested min/max values: {min_}/{max_}")
+    def process_decimal_field_type_to_pd_dtype(self) -> 'Dtype':
+        import numpy as np
+
+        decimal_constraints =\
+            cast(Optional[RecordsSchemaFieldDecimalConstraints], self.constraints)
+        if decimal_constraints:
+            if (decimal_constraints.fixed_precision is not None and
+                    decimal_constraints.fixed_scale is not None):
+                logger.warning("Pandas doesn't support a fixed precision type - "
+                               "using np.float64")
+                return np.float64
+            elif (decimal_constraints.fp_total_bits is not None and
+                    decimal_constraints.fp_significand_bits is not None):
+                if (decimal_constraints.fp_total_bits <= 16 and
+                        decimal_constraints.fp_significand_bits <= FLOAT16_SIGNIFICAND_BITS):
+                    return np.float16
+                elif (decimal_constraints.fp_total_bits <= 32 and
+                        decimal_constraints.fp_significand_bits <= FLOAT32_SIGNIFICAND_BITS):
+                    return np.float32
+                elif (decimal_constraints.fp_total_bits <= 64 and
+                        decimal_constraints.fp_significand_bits <= FLOAT64_SIGNIFICAND_BITS):
+                    return np.float64
+                elif (decimal_constraints.fp_total_bits <= 80 and
+                        decimal_constraints.fp_significand_bits <= FLOAT80_SIGNIFICAND_BITS):
                     return np.float128
-            else:
-                logger.warning(f"No integer constraints provided for field '{self.name}'; "
-                               "using int64")
-                if has_extension_types:
-                    return pd.Int64Dtype()
                 else:
-                    return np.int64
-        elif self.field_type == 'decimal':
-            decimal_constraints =\
-                cast(Optional[RecordsSchemaFieldDecimalConstraints], self.constraints)
-            if decimal_constraints:
-                if (decimal_constraints.fixed_precision is not None and
-                   decimal_constraints.fixed_scale is not None):
-                    logger.warning("Pandas doesn't support a fixed precision type - "
-                                   "using np.float64")
-                    return np.float64
-                elif (decimal_constraints.fp_total_bits is not None and
-                      decimal_constraints.fp_significand_bits is not None):
-                    if (decimal_constraints.fp_total_bits <= 16 and
-                       decimal_constraints.fp_significand_bits <= FLOAT16_SIGNIFICAND_BITS):
-                        return np.float16
-                    elif (decimal_constraints.fp_total_bits <= 32 and
-                          decimal_constraints.fp_significand_bits <= FLOAT32_SIGNIFICAND_BITS):
-                        return np.float32
-                    elif (decimal_constraints.fp_total_bits <= 64 and
-                          decimal_constraints.fp_significand_bits <= FLOAT64_SIGNIFICAND_BITS):
-                        return np.float64
-                    elif (decimal_constraints.fp_total_bits <= 80 and
-                          decimal_constraints.fp_significand_bits <= FLOAT80_SIGNIFICAND_BITS):
-                        return np.float128
-                    else:
-                        logger.warning("Downgrading float type to np.float128.  "
-                                       "Requested total bits: "
-                                       f"{decimal_constraints.fp_total_bits}.  "
-                                       "Requested significand bits: "
-                                       f"{decimal_constraints.fp_significand_bits}")
-                        return np.float128
-
-            logger.warning(f"No decimal constraints provided for field '{self.name}'; "
-                           "using float64")
-            return np.float64
-        elif self.field_type == 'boolean':
-            return np.bool_
-        elif self.field_type == 'string':
-            return np.object_
-        elif self.field_type == 'date':
-            return np.object_
-        elif self.field_type == 'datetime':
-            return 'datetime64[ns]'
-        elif self.field_type == 'datetimetz':
-            return 'datetime64[ns, UTC]'
-        elif self.field_type == 'time':
-            return np.object_
-        elif self.field_type == 'timetz':
-            return np.object_
-        else:
+                    logger.warning("Downgrading float type to np.float128.  "
+                                   "Requested total bits: "
+                                   f"{decimal_constraints.fp_total_bits}.  "
+                                   "Requested significand bits: "
+                                   f"{decimal_constraints.fp_significand_bits}")
+                    return np.float128
+
+        logger.warning(f"No decimal constraints provided for field '{self.name}'; "
+                       "using float64")
+        return np.float64
+
+    def to_pandas_dtype(self) -> 'Dtype':
+        import numpy as np
+
+        field_type_to_pd_dtype_map = {
+            'integer': self.process_integer_field_type_to_pd_dtype,
+            'decimal': self.process_decimal_field_type_to_pd_dtype,
+            'boolean': np.bool_,
+            'string': np.object_,
+            'date': np.object_,
+            'datetime': 'datetime64[ns]',
+            'datetimetz': 'datetime64[ns, UTC]',
+            'time': np.object_,
+            'timetz': np.object_,
+        }
+
+        pd_dtype = field_type_to_pd_dtype_map.get(self.field_type)
+        if not pd_dtype:
             raise NotImplementedError("Teach me how to handle records schema "
                                       f"type {self.field_type}")
+        if self.field_type in ('integer', 'decimal') and callable(pd_dtype):
+            pd_dtype = pd_dtype()
+
+        return pd_dtype
 
     def to_data(self) -> 'FieldDict':
         out: 'FieldDict' = {'type': self.field_type}