Manipulating Python Magic Methods

I have more of a background with data science libraries or calling methods and attributes from classes. I am experimenting with manipulating magic methods. I am having a difficult time getting bool types and returning their opposites.

bool

I did something with str and datetime objects that worked but can't seem to to the same with __cmp__, __lt__, __eq__ or `gt'. Here is my code:

str

datetime

__cmp__

__lt__

__eq__

class Opposite:

def __cmp__(self, other):

if other.__class__.__name__ == 'bool':
return other

def __lt__(self, other):
if other.__class__.__name__ == 'bool':
return other

def __eq__(self, other):
if other.__class__.__name__ == 'bool':
return other

def __gt__(self, other):
if other.__class__.__name__ == 'bool':
return other


if __name__=="__main__":

""" test class Compare """

a = 1
b = 1
c = a < b
d = a > b
e = a == b

print("Results:natnbtnctndtnetn".format(a,b,c,d,e))
print("nType:na-typetnb-typetnc-typetnd-typetne-typetn"
.format(type(a),type(b),type(c),type(d),type(e)))


This prints the following:

Results:
a 1
b 1
c False
d False
e True

Type:
a-type <class 'int'>
b-type <class 'int'>
c-type <class 'bool'>
d-type <class 'bool'>
e-type <class 'bool'>


As you can see, the results are the same as not using the class at all. I added an __init__ method to print using Opposite and it only prints that if I instantiate the object with something like a = Opposite().

__init__

using Opposite

a = Opposite()

I would like to enter something like a > b, a < b, or a == b, and return the opposite boolean value, True, or False, as an exercise.

a > b

a < b

a == b

True

False

I tried several things such as placing the methods under the __init__ method I created, which didn't work either. I read on this and still don't quite understand how to do this with booleans, integers and floats for that matter. The way the methods are above is how I was able to turn datetime objects into strings with __add__, __radd__ and __rsub__ methods.

__init__

__add__

__radd__

__rsub__

Thank you for your help.

EDIT

Thanks to your help, I have a better understanding and have completed my small experiment with this code:

class Opposite:

def __init__(self, x):
self._x = x

def __lt__(self, other):
return not self._x < other._x

def __eq__(self, other):
return not self._x == other._x

def __gt__(self, other):
return not self._x > other._x

def __le__(self, other):
return not self._x <= other._x

def __ge__(self, other):
return not self._x >= other._x

def tester(w, x, y, z):
try:
# Original values
a = w < x
b = w > x
c = w == x
d = w <= x
e = w >= x

# Opposite values
f = y < z
g = y > z
h = y == z
i = y <= z
j = y >= z

# Results
k = 'Fail' if a == f else 'Success'
l = 'Fail' if b == g else 'Success'
m = 'Fail' if c == h else 'Success'
n = 'Fail' if d == i else 'Success'
o = 'Fail' if e == j else 'Success'

print('nComparing and :t<t>t==t<=t>='.format(w, x))
print('Original Values:', end='t')
print('0t1t2t3t4'.format(a, b, c, d, e))
print('Opposite Values:', end='t')
print('0t1t2t3t4'.format(f, g, h, i, j))
print('Comparisons:', end='t')
print('t0t1t2t3t4'.format(k, l, m, n, o))

except(Exception) as err:
print(err)

if __name__=="__main__":

""" test class Compare """

a = 1
b = 2
c = Opposite(a)
d = Opposite(b)
tester(a, b, c, d)


This prints the following:

Comparing 1 and 2: < > == <= >=
Original Values: True False False True False
Opposite Values: False True True False True
Comparisons: Success Success Success Success Success


Opposite

__cmp__

int

NotImplemented

NotImplemented

__lt__

2 < 1

True

1 Answer
1

If you mean that you want to return the negation of the boolean resulting from the comparison you could do something like

class T:
def __init__(self, x):
self._x = x

def __lt__(self, other):
return not self._x < other._x

t1 = T(1)
t2 = T(2)

print(t1 < t2) #False


Note that in the comparison self._x < other._x you are using the __lt__ method of the int class.

self._x < other._x

__lt__

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