Collection of Utilities
Project description
WorkToy
Collection of General Utilities
pip install worktoy
The None-aware 'maybe'
In a programming language which shall rename nameless as well as typeless, the following syntax is available:
const func = (arg = null) => {
let val1 = arg || 1.0;
let val2 = arg ?? 1.0;
return [val1, val2]; }
In the above code, the default argument is set to null (in this context
null is treated the same as None in Python). The ??
operator is the
null-coalescence operator, which is nearly the same as the or
operator.
Consider the return value obtained from calling func()
:
func()
>>> (2) [1, 1]
This makes sense, but what happens when we call the function on a falsy value other than null, such as 0:
func(0)
>>> (3) [1, 0]
The first value in the return value comes from using the pipes (the logical or operator), is not aware of the difference between null and other falsy values. The null-coalescence operator is able to tell the difference. The WorkToy module brings this to python along with several derived utility functions:
maybe
In the below python code, we implement the same function using the maybe function from WorkToy:
def func(arg: Any = None) -> Any:
"""Function using the maybe from the WorkToy module"""
val1 = arg or 1.0
val2 = maybe(arg, 1.0)
return [val1, val2]
The implementation of maybe simply follows a common pattern:
def maybe(*args) -> Any:
"""Implementation of maybe returns the first argument given that
is different from None. If no such argument is found None is
returned."""
for arg in args:
if arg is not None:
return arg
return None
Unlike the ??
operator, the maybe
operator handles an arbitrary
number of arguments.
maybeType
The first of the derived functions finds the first argument of a particular type:
def maybeType(type_: type, *args) -> type_:
"""Returns the first argument of given type"""
maybeTypes
Adding an 's' returns every argument of given type. Further, it supports
keyword arguments pad: int
and padChar: Any
. If pad
is given it
defines the length of the returned list padded with padChar
or None
by default. Setting pad
will either pad or crop as necessary.
searchKeys
A common way to handle optional keyword arguments is something like:
def func(*args, **kwargs) -> Any:
"""Common function accepting arbitrary positional and keyword
arguments."""
val = kwargs.get('key', defaultValue)
...
In the above code, the get
function is used to look for a given key in
the collection of keyword arguments along with a (optional) default value.
Instead, searchKeys
allows for multiple keys in order of priority:
def func(*args, **kwargs) -> Any:
"""Common function accepting arbitrary positional and keyword
arguments."""
dV = defaultValue
val = searchKeys('k1', 'k2', 'k3', **kwargs)
...
In addition, WorkToy provides the following syntactic pork-scratchings for the keto-aware programmer:
def func(*args, **kwargs) -> Any:
"""Common function accepting arbitrary positional and keyword
arguments."""
dV = defaultValue
val = searchKeys('k1', 'k2', 'k3') @ int >> (kwargs, dV)
...
The matrix multiplication operator @
sets a type requirement and the
right-shift operator >>
invokes the search. The default value is then
given as the second positional argument in the tuple. Please note that
absense of **
. This causes kwargs
to be treated as a dictionary
entirely contained at the first positional argument. If invoked without a
default value, the parentheses may be omitted.
CallMeMaybe
This abstract baseclass registers any callable object as an instance.
This makes it stronger than the built-in callable
and even the
Callable
from the typing
package. If a custom class implements the
__call__
method, instances of this class may still not be recognized as
callable by the mentioned methods.
class FilteredClass:
"""A class requiring a callable filter before invoking some other
function"""
def __init__(self, *args, **kwargs) -> None:
filterKwarg = searchKeys('filter') @ CallMeMaybe >> kwargs
filterArg = maybeType(CallMeMaybe, *args)
filterDefault = lambda *arg, **kwargs: (arg, kwargs)
self._filter = maybe(filterKwarg, filterArg, filterDefault)
self._func = someFunction
def __call__(self, *args, **kwargs) -> Any:
"""Invokes some underlying function subject to the filter"""
return self._func(self._filter(*args, **kwargs))
Additionally, decorate functions with CallMeMaybe
to explicitly flag
functions as being instances of CallMeMaybe
. As expected, instances of
subclasses of CallMeMaybe
are regarded as instances.
String Tools
WorkToy also brings a number of convenient string related functions:
stringList
Consider the following code:
numbers = ['one', 'two', 'three', 'four']
The above involve repeated use of '
. On the Danish keyboard layout, the
'
key is located as indicated jklæø'
, meaning that the right pinky
finger must leap over two other keys. Instead, use stringList
:
numbers = stringList('one, two, three, four', )
>>> ['one', 'two', 'three', 'four']
monoSpace
Consider the following code:
msg = """Hello there! I am writing a long string right here in python
that stretches in length beyond the allowable line length. Thankfully,
we have the triple quotation mark syntax for indication of longer
strings."""
The above code takes things literally meaning that new lines are inserted.
Thus, in between 'python' at the end of the first line and 'that' at the
beginning of the second line, a '\n'
has been inserted. Instead, use
monoSpace
:
msgLine = monoSpace(msg) # msg as defined above
Now msgLine
contains now new lines and no repeated spaces. To
explicitly set a line break in the string, insert '<br>'
in the text.
Set a different string to denote a line break, give that string as the
second argument.
rawLines = """This is the first line. <br> Here is the second line.
Don't worry about the extra spaces surrounding the tag, they are
removed. """
twoLines = monoSpace(rawLines)
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