from __future__ import annotations
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from typing import Literal
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import numpy as np
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from pandas._libs import lib
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from pandas._typing import (
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DateTimeErrorChoices,
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DtypeBackend,
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npt,
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)
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from pandas.util._validators import check_dtype_backend
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from pandas.core.dtypes.cast import maybe_downcast_numeric
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from pandas.core.dtypes.common import (
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ensure_object,
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is_bool_dtype,
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is_datetime_or_timedelta_dtype,
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is_decimal,
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is_integer_dtype,
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is_number,
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is_numeric_dtype,
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is_scalar,
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is_string_dtype,
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needs_i8_conversion,
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)
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from pandas.core.dtypes.generic import (
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ABCIndex,
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ABCSeries,
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)
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import pandas as pd
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from pandas.core.arrays import BaseMaskedArray
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from pandas.core.arrays.string_ import StringDtype
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def to_numeric(
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arg,
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errors: DateTimeErrorChoices = "raise",
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downcast: Literal["integer", "signed", "unsigned", "float"] | None = None,
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dtype_backend: DtypeBackend | lib.NoDefault = lib.no_default,
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):
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"""
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Convert argument to a numeric type.
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The default return dtype is `float64` or `int64`
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depending on the data supplied. Use the `downcast` parameter
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to obtain other dtypes.
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Please note that precision loss may occur if really large numbers
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are passed in. Due to the internal limitations of `ndarray`, if
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numbers smaller than `-9223372036854775808` (np.iinfo(np.int64).min)
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or larger than `18446744073709551615` (np.iinfo(np.uint64).max) are
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passed in, it is very likely they will be converted to float so that
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they can be stored in an `ndarray`. These warnings apply similarly to
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`Series` since it internally leverages `ndarray`.
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Parameters
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----------
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arg : scalar, list, tuple, 1-d array, or Series
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Argument to be converted.
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errors : {'ignore', 'raise', 'coerce'}, default 'raise'
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- If 'raise', then invalid parsing will raise an exception.
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- If 'coerce', then invalid parsing will be set as NaN.
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- If 'ignore', then invalid parsing will return the input.
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downcast : str, default None
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Can be 'integer', 'signed', 'unsigned', or 'float'.
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If not None, and if the data has been successfully cast to a
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numerical dtype (or if the data was numeric to begin with),
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downcast that resulting data to the smallest numerical dtype
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possible according to the following rules:
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- 'integer' or 'signed': smallest signed int dtype (min.: np.int8)
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- 'unsigned': smallest unsigned int dtype (min.: np.uint8)
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- 'float': smallest float dtype (min.: np.float32)
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As this behaviour is separate from the core conversion to
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numeric values, any errors raised during the downcasting
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will be surfaced regardless of the value of the 'errors' input.
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In addition, downcasting will only occur if the size
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of the resulting data's dtype is strictly larger than
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the dtype it is to be cast to, so if none of the dtypes
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checked satisfy that specification, no downcasting will be
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performed on the data.
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dtype_backend : {"numpy_nullable", "pyarrow"}, defaults to NumPy backed DataFrames
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Which dtype_backend to use, e.g. whether a DataFrame should have NumPy
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arrays, nullable dtypes are used for all dtypes that have a nullable
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implementation when "numpy_nullable" is set, pyarrow is used for all
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dtypes if "pyarrow" is set.
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The dtype_backends are still experimential.
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.. versionadded:: 2.0
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Returns
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-------
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ret
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Numeric if parsing succeeded.
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Return type depends on input. Series if Series, otherwise ndarray.
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See Also
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--------
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DataFrame.astype : Cast argument to a specified dtype.
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to_datetime : Convert argument to datetime.
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to_timedelta : Convert argument to timedelta.
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numpy.ndarray.astype : Cast a numpy array to a specified type.
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DataFrame.convert_dtypes : Convert dtypes.
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Examples
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--------
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Take separate series and convert to numeric, coercing when told to
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>>> s = pd.Series(['1.0', '2', -3])
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>>> pd.to_numeric(s)
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0 1.0
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1 2.0
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2 -3.0
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dtype: float64
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>>> pd.to_numeric(s, downcast='float')
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0 1.0
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1 2.0
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2 -3.0
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dtype: float32
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>>> pd.to_numeric(s, downcast='signed')
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0 1
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1 2
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2 -3
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dtype: int8
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>>> s = pd.Series(['apple', '1.0', '2', -3])
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>>> pd.to_numeric(s, errors='ignore')
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0 apple
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1 1.0
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2 2
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3 -3
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dtype: object
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>>> pd.to_numeric(s, errors='coerce')
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0 NaN
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1 1.0
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2 2.0
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3 -3.0
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dtype: float64
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Downcasting of nullable integer and floating dtypes is supported:
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>>> s = pd.Series([1, 2, 3], dtype="Int64")
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>>> pd.to_numeric(s, downcast="integer")
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0 1
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1 2
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2 3
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dtype: Int8
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>>> s = pd.Series([1.0, 2.1, 3.0], dtype="Float64")
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>>> pd.to_numeric(s, downcast="float")
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0 1.0
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1 2.1
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2 3.0
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dtype: Float32
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"""
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if downcast not in (None, "integer", "signed", "unsigned", "float"):
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raise ValueError("invalid downcasting method provided")
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if errors not in ("ignore", "raise", "coerce"):
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raise ValueError("invalid error value specified")
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check_dtype_backend(dtype_backend)
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is_series = False
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is_index = False
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is_scalars = False
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if isinstance(arg, ABCSeries):
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is_series = True
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values = arg.values
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elif isinstance(arg, ABCIndex):
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is_index = True
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if needs_i8_conversion(arg.dtype):
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values = arg.view("i8")
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else:
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values = arg.values
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elif isinstance(arg, (list, tuple)):
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values = np.array(arg, dtype="O")
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elif is_scalar(arg):
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if is_decimal(arg):
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return float(arg)
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if is_number(arg):
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return arg
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is_scalars = True
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values = np.array([arg], dtype="O")
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elif getattr(arg, "ndim", 1) > 1:
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raise TypeError("arg must be a list, tuple, 1-d array, or Series")
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else:
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values = arg
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orig_values = values
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# GH33013: for IntegerArray & FloatingArray extract non-null values for casting
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# save mask to reconstruct the full array after casting
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mask: npt.NDArray[np.bool_] | None = None
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if isinstance(values, BaseMaskedArray):
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mask = values._mask
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values = values._data[~mask]
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values_dtype = getattr(values, "dtype", None)
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if isinstance(values_dtype, pd.ArrowDtype):
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mask = values.isna()
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values = values.dropna().to_numpy()
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new_mask: np.ndarray | None = None
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if is_numeric_dtype(values_dtype):
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pass
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elif is_datetime_or_timedelta_dtype(values_dtype):
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values = values.view(np.int64)
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else:
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values = ensure_object(values)
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coerce_numeric = errors not in ("ignore", "raise")
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try:
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values, new_mask = lib.maybe_convert_numeric( # type: ignore[call-overload] # noqa
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values,
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set(),
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coerce_numeric=coerce_numeric,
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convert_to_masked_nullable=dtype_backend is not lib.no_default
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or isinstance(values_dtype, StringDtype),
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)
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except (ValueError, TypeError):
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if errors == "raise":
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raise
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values = orig_values
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if new_mask is not None:
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# Remove unnecessary values, is expected later anyway and enables
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# downcasting
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values = values[~new_mask]
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elif (
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dtype_backend is not lib.no_default
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and new_mask is None
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or isinstance(values_dtype, StringDtype)
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):
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new_mask = np.zeros(values.shape, dtype=np.bool_)
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# attempt downcast only if the data has been successfully converted
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# to a numerical dtype and if a downcast method has been specified
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if downcast is not None and is_numeric_dtype(values.dtype):
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typecodes: str | None = None
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if downcast in ("integer", "signed"):
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typecodes = np.typecodes["Integer"]
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elif downcast == "unsigned" and (not len(values) or np.min(values) >= 0):
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typecodes = np.typecodes["UnsignedInteger"]
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elif downcast == "float":
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typecodes = np.typecodes["Float"]
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# pandas support goes only to np.float32,
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# as float dtypes smaller than that are
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# extremely rare and not well supported
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float_32_char = np.dtype(np.float32).char
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float_32_ind = typecodes.index(float_32_char)
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typecodes = typecodes[float_32_ind:]
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if typecodes is not None:
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# from smallest to largest
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for typecode in typecodes:
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dtype = np.dtype(typecode)
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if dtype.itemsize <= values.dtype.itemsize:
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values = maybe_downcast_numeric(values, dtype)
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# successful conversion
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if values.dtype == dtype:
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break
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# GH33013: for IntegerArray, BooleanArray & FloatingArray need to reconstruct
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# masked array
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if (mask is not None or new_mask is not None) and not is_string_dtype(values.dtype):
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if mask is None or (new_mask is not None and new_mask.shape == mask.shape):
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# GH 52588
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mask = new_mask
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else:
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mask = mask.copy()
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assert isinstance(mask, np.ndarray)
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data = np.zeros(mask.shape, dtype=values.dtype)
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data[~mask] = values
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from pandas.core.arrays import (
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ArrowExtensionArray,
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BooleanArray,
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FloatingArray,
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IntegerArray,
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)
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klass: type[IntegerArray] | type[BooleanArray] | type[FloatingArray]
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if is_integer_dtype(data.dtype):
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klass = IntegerArray
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elif is_bool_dtype(data.dtype):
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klass = BooleanArray
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else:
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klass = FloatingArray
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values = klass(data, mask)
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if dtype_backend == "pyarrow" or isinstance(values_dtype, pd.ArrowDtype):
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values = ArrowExtensionArray(values.__arrow_array__())
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if is_series:
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return arg._constructor(values, index=arg.index, name=arg.name)
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elif is_index:
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# because we want to coerce to numeric if possible,
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# do not use _shallow_copy
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return pd.Index(values, name=arg.name)
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elif is_scalars:
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return values[0]
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else:
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return values
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