CODEWITHSUNDEEP
pythonmethodsiteration
user1175133
user1175133

Reputation: 51

Creating a list of methods to be executed in Python

How can I create a list of methods in python to be applied to an object?

Given some arbitrary class:

class someClass:
    def __init__(self, s):
        self.size = s

    def shrink(self):
        self.size -= 1

    def grow(self):
        self.size += 1

    def invert(self):
        self.size = -self.size

I want to be able to write an iterable object like this list:

instructions = [shrink, grow, shrink, shrink, grow, invert]

To be run through a for-loop later:

elephant = someClass(90)
sizeList = []
for ins in instructions:
    elephant.ins()
    sizeList.append(elephant.size)

I've done something similar with functions before. Not being able to do this with methods would require me to rewrite an intimidating amount of code...

Upvotes: 1

Views: 1392

Answers (4)

Joran Beasley
Joran Beasley

Reputation: 114098

You could create a list of the method names then use getattr() to access the methods:

instructions = ["shrink", "grow", "shrink"]
for i in instructions:
     getattr(elephant, i)()

Upvotes: 6

phihag
phihag

Reputation: 288280

You can use dir to get all property names of an object, and getattr to get a property value of an object. You may also want to not call any non-callable properties (such as 2 or "foo"):

for m in dir(elephant):
    if not m.startswith('_'):
        f = getattr(elephant, m)
        if callable(f): # Do not try to call non-function properties
            f()

Upvotes: 0

Andrew Clark
Andrew Clark

Reputation: 208695

As an alternative to using strings for your list of instructions, you could do the following:

instructions = [someClass.shrink, someClass.grow, someClass.shrink,
                someClass.shrink, someClass.grow, someClass.invert]
elephant = someClass(90)
sizeList = []
for ins in instructions:
    ins(elephant)
    sizeList.append(elephant.size)

Upvotes: 3

kojiro
kojiro

Reputation: 77167

Possibly naïvely:

for ins in instructions:
  getattr(elephant, ins)()

Gotchas include that ins must be a string and that it's probably wise to validate both that ins is what you really want to call and that getattr(elephant, ins) is a callable.

Upvotes: 0

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