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+--- Thread: question about __repr__ in a class (/thread-41407.html)
question about __repr__ in a class - akbarza - Jan-11-2024
hi
the below code is in:https://realpython.com/python-mutable-vs-immutable-types/#techniques-to-control-mutability-in-custom-classes
class Point:
def __init__(self, x, y):
self._x = x
self._y = y
@property
def x(self):
return self._x
@property
def y(self):
return self._y
def __repr__(self):
return f"{type(self).__name__}(x={self.x}, y={self.y})"what does the last line do also what does the __repe__ method do? how can i use the __repr__ method? if it is omitted, does it cause any problems?thanks
RE: question about __repr__ in a class - deanhystad - Jan-11-2024
Objects have two string representations: __str__ is the pretty one, and __repr__ is the smart one. __str__ is used when you call str() or print() an object. __repr__ is used when you call repr() or when you print an object as part of a collection (list, dictionary, set, tuple).
Have you tried omitting the method to see what happens? What do you think will happen?
RE: question about __repr__ in a class - Gribouillis - Jan-11-2024
Don't forget to use the search field in the Python documentation
RE: question about __repr__ in a class - akbarza - Jan-12-2024
(Jan-11-2024, 12:14 PM)deanhystad Wrote: Objects have two string representations: __str__ is the pretty one, and __repr__ is the smart one. __str__ is used when you call str() or print() an object. __repr__ is used when you call repr() or when you print an object as part of a collection (list, dictionary, set, tuple).
Have you tried omitting the method to see what happens? What do you think will happen?
hi
i omitted it, but i did not see any change. what can i write or add to the above code too see the changes occure with ommitting the __repr__ method?
thanks again for reply
RE: question about __repr__ in a class - DeaD_EyE - Jan-12-2024
If the method
__str__ is not available, then __repr__ is called instead.If you just want a class with some variables and a nice representation, you could use dataclasses instead:
import math
from dataclasses import dataclass
@dataclass
class PointD:
x: int
y: int
@property
def alpha(self):
"""
alpha for polar coordinates
"""
return math.degrees(math.atan2(self.y, self.x))
@property
def hypot(self):
"""
Length of hypot
"""
return math.hypot(self.x, self.y)
@property
def polar(self):
"""
Poloar coordinates
"""
return self.alpha, self.hypot
@classmethod
def from_ploar(cls, polar):
"""
Create a point from ploar coordinates
polar := (alpha, hypot)
"""
alpha = math.radians(polar[0])
return cls(math.cos(alpha) * polar[1], math.sin(alpha) * polar[1])
p2 = PointD(7, 9)
print(p2)
print(f"{p2!s}")
print(f"{p2!r}")
print(f"{p2.alpha}")
print(f"{p2.hypot}")
print(f"{p2.polar}")
print(PointD.from_ploar(p2.polar))Output:PointD(x=7, y=9)
PointD(x=7, y=9)
PointD(x=7, y=9)
52.1250163489018
11.40175425099138
(52.1250163489018, 11.40175425099138)
PointD(x=6.999999999999998, y=9.0)