laywerrobot/lib/python3.6/site-packages/pandas/errors/__init__.py
2020-08-27 21:55:39 +02:00

184 lines
5.4 KiB
Python

# flake8: noqa
"""
Expose public exceptions & warnings
"""
from pandas._libs.tslib import OutOfBoundsDatetime
class PerformanceWarning(Warning):
"""
Warning raised when there is a possible
performance impact.
"""
class UnsupportedFunctionCall(ValueError):
"""
Exception raised when attempting to call a numpy function
on a pandas object, but that function is not supported by
the object e.g. ``np.cumsum(groupby_object)``.
"""
class UnsortedIndexError(KeyError):
"""
Error raised when attempting to get a slice of a MultiIndex,
and the index has not been lexsorted. Subclass of `KeyError`.
.. versionadded:: 0.20.0
"""
class ParserError(ValueError):
"""
Exception that is raised by an error encountered in `pd.read_csv`.
"""
class DtypeWarning(Warning):
"""
Warning raised when reading different dtypes in a column from a file.
Raised for a dtype incompatibility. This can happen whenever `read_csv`
or `read_table` encounter non-uniform dtypes in a column(s) of a given
CSV file.
See Also
--------
pandas.read_csv : Read CSV (comma-separated) file into a DataFrame.
pandas.read_table : Read general delimited file into a DataFrame.
Notes
-----
This warning is issued when dealing with larger files because the dtype
checking happens per chunk read.
Despite the warning, the CSV file is read with mixed types in a single
column which will be an object type. See the examples below to better
understand this issue.
Examples
--------
This example creates and reads a large CSV file with a column that contains
`int` and `str`.
>>> df = pd.DataFrame({'a': (['1'] * 100000 + ['X'] * 100000 +
... ['1'] * 100000),
... 'b': ['b'] * 300000})
>>> df.to_csv('test.csv', index=False)
>>> df2 = pd.read_csv('test.csv')
... # DtypeWarning: Columns (0) have mixed types
Important to notice that ``df2`` will contain both `str` and `int` for the
same input, '1'.
>>> df2.iloc[262140, 0]
'1'
>>> type(df2.iloc[262140, 0])
<class 'str'>
>>> df2.iloc[262150, 0]
1
>>> type(df2.iloc[262150, 0])
<class 'int'>
One way to solve this issue is using the `dtype` parameter in the
`read_csv` and `read_table` functions to explicit the conversion:
>>> df2 = pd.read_csv('test.csv', sep=',', dtype={'a': str})
No warning was issued.
>>> import os
>>> os.remove('test.csv')
"""
class EmptyDataError(ValueError):
"""
Exception that is thrown in `pd.read_csv` (by both the C and
Python engines) when empty data or header is encountered.
"""
class ParserWarning(Warning):
"""
Warning raised when reading a file that doesn't use the default 'c' parser.
Raised by `pd.read_csv` and `pd.read_table` when it is necessary to change
parsers, generally from the default 'c' parser to 'python'.
It happens due to a lack of support or functionality for parsing a
particular attribute of a CSV file with the requested engine.
Currently, 'c' unsupported options include the following parameters:
1. `sep` other than a single character (e.g. regex separators)
2. `skipfooter` higher than 0
3. `sep=None` with `delim_whitespace=False`
The warning can be avoided by adding `engine='python'` as a parameter in
`pd.read_csv` and `pd.read_table` methods.
See Also
--------
pd.read_csv : Read CSV (comma-separated) file into DataFrame.
pd.read_table : Read general delimited file into DataFrame.
Examples
--------
Using a `sep` in `pd.read_csv` other than a single character:
>>> import io
>>> csv = u'''a;b;c
... 1;1,8
... 1;2,1'''
>>> df = pd.read_csv(io.StringIO(csv), sep='[;,]')
... # ParserWarning: Falling back to the 'python' engine...
Adding `engine='python'` to `pd.read_csv` removes the Warning:
>>> df = pd.read_csv(io.StringIO(csv), sep='[;,]', engine='python')
"""
class MergeError(ValueError):
"""
Error raised when problems arise during merging due to problems
with input data. Subclass of `ValueError`.
"""
class NullFrequencyError(ValueError):
"""
Error raised when a null `freq` attribute is used in an operation
that needs a non-null frequency, particularly `DatetimeIndex.shift`,
`TimedeltaIndex.shift`, `PeriodIndex.shift`.
"""
class AccessorRegistrationWarning(Warning):
"""Warning for attribute conflicts in accessor registration."""
class AbstractMethodError(NotImplementedError):
"""Raise this error instead of NotImplementedError for abstract methods
while keeping compatibility with Python 2 and Python 3.
"""
def __init__(self, class_instance, methodtype='method'):
types = {'method', 'classmethod', 'staticmethod', 'property'}
if methodtype not in types:
msg = 'methodtype must be one of {}, got {} instead.'.format(
methodtype, types)
raise ValueError(msg)
self.methodtype = methodtype
self.class_instance = class_instance
def __str__(self):
if self.methodtype == 'classmethod':
name = self.class_instance.__name__
else:
name = self.class_instance.__class__.__name__
msg = "This {methodtype} must be defined in the concrete class {name}"
return (msg.format(methodtype=self.methodtype, name=name))