Regarding inplace operations apart from increment/decrement/multiply/divide

Python Help
1

When we want to do an in place increment/decrement/…
We could use something like this,

a = 1
a += 1

and then,

print(a)

gives

2

but, if I have a string and I want to make it upper case, then, I need to do something like,

attribute = 'abc'
attribute = attribute.upper()

I need to use the attribute term on the right side also.
what could be the reason for there being no,

attribute.upper(in_place=True)

so that repeating the same term on the right side could be avoided.
this applies for other methods also, like attribute.lower()

or, let us say, I want to do something like,

attribute_2 = ['abc', 'def']
attribute_2 = list(map(lambda x: x.upper(), attribute_2))

then, again, I need to specify, attribute_2 on the right side.
what could be a way to avoid using the same term on the right side?

2

Integers and strings are immutable. Methods like some_string.upper(inplace=True) can never exist. Also, the “in-place increment” a+=1 isn’t really in-place, it’s just short for a=a+1. To check this:

a = 42
b = a
assert a is b  # check that a and b are the same int object
a += 1
print(a, b)  # prints 43 42 because `b` hasn't changed

If you could mutate the integer 42 in-place to become 43, then that last print would show “43 43”.

As for lists, in principle there could exist mutating methods like my_list.replace_each(lambda x: x.upper()), but AFAIK you need to “specify the name of the variable on both sides of the assignment operator” as you said.

BTW, instead of list(map(...)), using list comprehensions is usually clearer:

mylist = [x.upper() for x in mylist]
1 Like
3

but if I implement my custom upper method, something like this,

class CustomString(str):
  def upper(self, in_place=False):
    if in_place==True:
      CustomString.__repr__ = lambda x: x.upper(in_place=True)
    return super().upper()

then,

a = CustomString('abc')
a.upper(in_place=True)

gives

'ABC'

and

a

gives,

ABC

but there is some implementation issue, as I changed the __repr__ itself, probably there would be a better way to implement it, as,

b = CustomString('aaa')
b

gives,

AAA

is there a way to create a custom mutable string?