pandas.to_numeric#

pandas.to_numeric(arg, errors='raise', downcast=None)[source]#

Convert argument to a numeric type.

The default return dtype is float64 or int64 depending on the data supplied. Use the downcast parameter to obtain other dtypes.

Please note that precision loss may occur if really large numbers are passed in. Due to the internal limitations of ndarray, if numbers smaller than -9223372036854775808 (np.iinfo(np.int64).min) or larger than 18446744073709551615 (np.iinfo(np.uint64).max) are passed in, it is very likely they will be converted to float so that they can stored in an ndarray. These warnings apply similarly to Series since it internally leverages ndarray.

Parameters

argscalar, list, tuple, 1-d array, or Series

Argument to be converted.

errors{‘ignore’, ‘raise’, ‘coerce’}, default ‘raise’

If ‘raise’, then invalid parsing will raise an exception.
If ‘coerce’, then invalid parsing will be set as NaN.
If ‘ignore’, then invalid parsing will return the input.

downcaststr, default None

Can be ‘integer’, ‘signed’, ‘unsigned’, or ‘float’. If not None, and if the data has been successfully cast to a numerical dtype (or if the data was numeric to begin with), downcast that resulting data to the smallest numerical dtype possible according to the following rules:

‘integer’ or ‘signed’: smallest signed int dtype (min.: np.int8)
‘unsigned’: smallest unsigned int dtype (min.: np.uint8)
‘float’: smallest float dtype (min.: np.float32)

As this behaviour is separate from the core conversion to numeric values, any errors raised during the downcasting will be surfaced regardless of the value of the ‘errors’ input.

In addition, downcasting will only occur if the size of the resulting data’s dtype is strictly larger than the dtype it is to be cast to, so if none of the dtypes checked satisfy that specification, no downcasting will be performed on the data.

Returns

ret: Numeric if parsing succeeded. Return type depends on input. Series if Series, otherwise ndarray.

See also

DataFrame.astype: Cast argument to a specified dtype.
to_datetime: Convert argument to datetime.
to_timedelta: Convert argument to timedelta.
numpy.ndarray.astype: Cast a numpy array to a specified type.
DataFrame.convert_dtypes: Convert dtypes.

Examples

Take separate series and convert to numeric, coercing when told to

>>> s = pd.Series(['1.0', '2', -3])
>>> pd.to_numeric(s)
0    1.0
1    2.0
2   -3.0
dtype: float64
>>> pd.to_numeric(s, downcast='float')
0    1.0
1    2.0
2   -3.0
dtype: float32
>>> pd.to_numeric(s, downcast='signed')
0    1
1    2
2   -3
dtype: int8
>>> s = pd.Series(['apple', '1.0', '2', -3])
>>> pd.to_numeric(s, errors='ignore')
0    apple
1      1.0
2        2
3       -3
dtype: object
>>> pd.to_numeric(s, errors='coerce')
0    NaN
1    1.0
2    2.0
3   -3.0
dtype: float64

Downcasting of nullable integer and floating dtypes is supported:

>>> s = pd.Series([1, 2, 3], dtype="Int64")
>>> pd.to_numeric(s, downcast="integer")
0    1
1    2
2    3
dtype: Int8
>>> s = pd.Series([1.0, 2.1, 3.0], dtype="Float64")
>>> pd.to_numeric(s, downcast="float")
0    1.0
1    2.1
2    3.0
dtype: Float32