Python question about overridden/redefined imported function as Class method

Question

In https://github.com/biopython/biopython/blob/518c4be6ae16f1e00bfd55781171da91282b340a/Bio/SeqUtils/ProtParam.py I have this importing statement:

from Bio.SeqUtils import molecular_weight

and then in a class:

class ProteinAnalysis:

.....
.....
    def molecular_weight(self):
        """Calculate MW from Protein sequence."""
        return molecular_weight(
            self.sequence, seq_type="protein", monoisotopic=self.monoisotopic
        )

......
......

What is this type of coding called? Is it normal to call imported function and class method with same name?

To my knowledge, self.molecular_weights is not equal to molecular_weights, but why call them the same? Is that PEP 8 compliant?

Would

a = ProteinAnalysis()

print(a.molecular_weights == molecular_weights)

give True or False?

What about:

print(a.molecular_weights(*args,**kwargs) == molecular_weights(*args, **kwargs))

Answer 1

Yes. This is normal as there is no contradiction. You cannot freely get access to any class attributes even in methods inside a class. For example, let's look at this:

var = 5

class SomeClass:
    var = 6

    def show(self):
        print(var)

SomeClass().show()

The result is 5. As there is only one "variable" var in global scope.

If we unlink it via del var, we will get NameError:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Input In [38], in <cell line: 1>()
----> 1 SomeClass.show()

Input In [37], in SomeClass.show()
      5 def show():
----> 6     print(var)

NameError: name 'var' is not defined

But you can get free access during the class initialisation:

class SomeClass:
    var = 6
    print(var)

    def show():
        print(var)

Hereinabove code prints 6.

In Biopython code only the imported function is used because the calling is inside a method where there is no direct access to the class attributes. Moreover, the method even is not initialised at the moment.

a.molecular_weights == molecular_weights gives False because even if they do the same they are different objects: a method & a function.

molecular_weights() == a.molecular_weights() would give True, if the same arguments are sent.

There is no contradiction with PEP8 naming rules as both do the same but one is a function, other is a method of appropriate class and objects.