Extension of Builtin Functions

Accessor

extepy.arggetter(*keys)

Return a callable object that fetches the argument(s) from its operand.

Parameters:

*keys (int | str) – If it is an int (can be negative), it is the index of the positional argument to be fetched. If it is a str, it is the name of keyword argument to be fetched.

Return type:

callable

Raises:

KeyError | IndexError – Raises when the argument is not found.

Examples

Get the first positional argument.

>>> getter = arggetter(0)
>>> getter("a", "b", "c", key="value")
'a'

Get the positional arguments and keyword arguments.

>>> getter = arggetter(-1, 0, 1, "key")
>>> getter("a", "b", "c", key="value")
('c', 'a', 'b', 'value')

Raise an error if the index is out of range.

>>> getter = arggetter(0, 1, 2)
>>> getter("A", key="value")
Traceback (most recent call last):
...
IndexError: positional argument index is out of range

Checker

extepy.argchecker(*keys)

Return a callable object to check the existences of argument(s).

Parameters:

*keys (int | str) – If it is an int (can be negative), it is the index of the positional argument to be fetched. If it is a str, it is the name of keyword argument to be fetched.

Return type:

bool | tuple[bool]

Examples

>>> getter = argchecker(-1, 0, 1, 5, "key", "other")
>>> getter("a", "b", "c", key="value")
(True, True, True, False, True, False)

extepy.attrchecker(*attrs)

Return a callable object to check the existence of the given attribute(s).

Parameters:

*attrs (str) – Attribute names.

Examples

>>> c = attrchecker("mro", "type")
>>> c(type)
(True, False)

>>> import os
>>> c = attrchecker("path", "path.sep", "sep.path")
>>> c(os)
(True, True, False)

extepy.itemchecker(*items)

Return a callable object to check the existence of the given item(s).

Examples

>>> data = {"name": {"first": "Zhiqing", "last": "Xiao"}, "city": "Beijing"}
>>> c = itemchecker(["name", "first"], ["name", "middle"], ["name", "last"], "city", "sex")
>>> c(data)
(True, False, True, True, False)

>>> itemchecker(-3, 0, 3)([1, 2, 3])
(True, True, False)

Factory

extepy.constantcreator(value, copy=False)

Callable that returns the same constant when it is called.

Parameters:

• value – Constant value to be returned.

• copy – If True, return a new copy of the constant value.

Returns:

Callable object that returns value, ignoring its parameters.

Return type:

callable

Examples

Always return the string "value".

>>> creator = constantcreator("value")
>>> creator()
'value'

Create a pd.DataFrame whose elements are all empty lists.

>>> import pandas as pd
>>> df = pd.DataFrame(index=range(3), columns=["A"])
>>> (df.map if hasattr(df, "map") else df.applymap)(constantcreator([]))
    A
0  []
1  []
2  []

Return a new copy when copy=True.

>>> import pandas as pd
>>> df = pd.DataFrame(index=range(3), columns=["A"])
>>> constantcreator(df, copy=True)() is df
False