Monkey Patching a String Python [duplicate]

Question

I am working on a python project and below is what I have:

mystring= 'Hello work'

and I want to write a function that replaces k with a m some thing like below:

def replace_alpha(string):
    return string.replace('k', 'm') # returns Hello worm

I wanted to use Monkey Patching on a string such that I can use it the below way:

string = 'Hello work'
string = string.replace_alpha()
print(string)   # prints Hello worm

instead of:

string = replace_alpha(string)

is this possible? Can I use monkey patching with a built-in rather can I extent the __builtins__?

That's not monkey patching. Monkey patching is the modification of an object from a different scope. — Klaus D.
– Klaus D., Commented Oct 25, 2018 at 7:37
@hspandher op stated that he doesnt want to touch __builtins__. — georgexsh
– georgexsh, Commented Oct 25, 2018 at 7:48

georgexsh · Accepted Answer · 2018-10-25 07:42:32Z

4

It is possible with forbiddenfruit library:

from forbiddenfruit import curse

def replace_alpha(string):
    return string.replace('k', 'm')

curse(str, "replace_alpha", replace_alpha)

s = 'Hello work'
print(s.replace_alpha())

answered Oct 25, 2018 at 7:42

georgexsh

16.8k3 gold badges45 silver badges71 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Erik Brendel Over a year ago

The wording of this library is beautiful :)

user2390182 · Accepted Answer · 2018-10-25 07:43:54Z

1

It is not possible so easily. You cannot set attributes of immutable str instances or the built-in str class. Without that capability, it is tough change their behaviour. You can, however, subclass str:

class PatchStr(str):
  def replace_alpha(self):
    return self.replace('k', 'm')

string = PatchStr('hello work')
string = string.replace_alpha()
string
# 'hello worm'

I don't think you can get much closer.

edited Oct 25, 2018 at 7:43

answered Oct 25, 2018 at 7:41

user2390182

73.7k6 gold badges71 silver badges95 bronze badges

4 Comments

Adam Smith Over a year ago

string remains "hello work", however.

user2390182 Over a year ago

@AdamSmith which it (the str object the method is called on) does in the OP's code, too. Of course, you have to reassign the return value.

Adam Smith Over a year ago

That's not how I understand the requested end state.

user2390182 Over a year ago

@AdamSmith string is just a variable name. The behaviour is the one stated by the OP. string = string.replace_alpha() in the original post indicates that they are not expecting to mutate the object.

Collectives™ on Stack Overflow

Monkey Patching a String Python [duplicate]

2 Answers 2

1 Comment

4 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

4 Comments

Linked

Related