How to use dunder methods for object comparison [closed]

Question

Comparing two objects using dunder methods

I was trying to compare two 'Time objects', but I got this error:

'TypeError: '<' not supported between instances of 'Time' and 'Time'

This is what I tried:

1. I First initialized the 'time Class'.

class Time:
    def __init__(self, h, m, s):
        self._h = h
        self._m = m
        self._s = s

    # Read-only field accessors
    @property
    def hours(self):
        return self._h

    @property
    def minutes(self):
        return self._m

    @property
    def seconds(self):
        return self._s

2. I created a method to compare the two Time objects.

def _cmp(time1, time2):
    if time1._h < time2._h:
        return 1
    if time1._h > time2._h:
        return -1
    if time1._m < time2._m:
        return 1
    if time1._m > time2._m:
        return -1
    if time1._s < time2._s:
        return 1
    if time1._s > time2._s:
        return -1
    else:
        return 0

3. I created the dunder methods.

def __eq__(self, other):
    return True if _cmp(self, other) == 0 else False

def __lt__(self, other):
    return True if _cmp(self, other) == 1 else False

def __le__(self, other):
    return True if _cmp(self, other) == 1 or _cmp(self, other) == 0 else False

4. I instantiated some objects, and tried comparing them (resulting in an error).

t1 = Time(13, 10, 5)
t2 = Time(5, 15, 30)

print(t1 < t2)
print(t2 <= t1)

I must surely be missing something. All tips on coding are welcome!

Answer 1

There are many dunder-methods (or magic-methods), if you want to use < and <= then you want to use __lt__ for < and __le__ for <= (stands for less-than and less-equal)

class A:
    def __init__(self, n):
        self.n = n

    def __le__(self, other):
        return self.n <= other.n

a = A(5)
b = A(10)
print(a <= b)

will return True, because 5 is smaller-or-equal to 10.

Answer 2

As Matthias and Jonathan suggested, I forgot to indent the following code and placed it outside my Time class:

def __eq__(self, other):
    return True if _cmp(self, other) == 0 else False

def __lt__(self, other):
    return True if _cmp(self, other) == 1 else False

def __le__(self, other):
    return True if _cmp(self, other) == 1 or _cmp(self, other) == 0 else False