An example of placeholder use:

from partial_apply import Empty, PartialFn, PartialMethod

isint = PartialFn(isinstance, Empty, int)

This makes a function isint() that takes one positional argument and returns True if it is an int and False otherwise. That is, calling isint(1) is equivalent to calling isinstance(1, int). The supplied positional arguments fill in Empty placeholder slots from left to right before reverting to functools.partial()-style appending.

An example of PartialMethod use:

count_true = PartialMethod('count', True)
count_true((False, True))  # returns 1
count_true([False, True])  # returns 1

This makes a function count_true() that counts the number of True values in a sequence. It looks up the sequence method count on the first argument and calls it with the single argument True. The calls shown are equivalent to (False, True).count(True) and [False, True].count(True). Since count_true() only stores the method name and not the method itself, it works on any type with a count() method.

Like PartialFn, PartialMethod supports placeholder positional arguments and functools.partial()-like keyword arguments.