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78 lines (57 loc) · 2.75 KB
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"""Class Definition Syntax.
@see: https://docs.python.org/3/tutorial/classes.html#class-objects
After defining the class attributes to a class, the class object can be created by assigning the
object to a variable. The created object would have instance attributes associated with it.
"""
def test_class_objects():
"""Class Objects.
Class objects support two kinds of operations:
- attribute references
- instantiation.
"""
# ATTRIBUTE REFERENCES use the standard syntax used for all attribute references in
# Python: obj.name. Valid attribute names are all the names that were in the class’s namespace
# when the class object was created. For class MyCounter the following references are valid
# attribute references:
class ComplexNumber:
"""Example of the complex numbers class"""
real = 0
imaginary = 0
def get_real(self):
"""Return real part of complex number."""
return self.real
def get_imaginary(self):
"""Return imaginary part of complex number."""
return self.imaginary
assert ComplexNumber.real == 0
# __doc__ is also a valid attribute, returning the docstring belonging to the class
assert ComplexNumber.__doc__ == 'Example of the complex numbers class'
# Class attributes can also be assigned to, so you can change the value of
# ComplexNumber.counter by assignment.
ComplexNumber.real = 10
assert ComplexNumber.real == 10
# CLASS INSTANTIATION uses function notation. Just pretend that the class object is a
# parameterless function that returns a new instance of the class. For example
# (assuming the above class):
complex_number = ComplexNumber()
assert complex_number.real == 10
assert complex_number.get_real() == 10
# Let's change counter default value back.
ComplexNumber.real = 10
assert ComplexNumber.real == 10
# The instantiation operation (“calling” a class object) creates an empty object. Many classes
# like to create objects with instances customized to a specific initial state. Therefore a
# class may define a special method named __init__(), like this:
class ComplexNumberWithConstructor:
"""Example of the class with constructor"""
def __init__(self, real_part, imaginary_part):
self.real = real_part
self.imaginary = imaginary_part
def get_real(self):
"""Return real part of complex number."""
return self.real
def get_imaginary(self):
"""Return imaginary part of complex number."""
return self.imaginary
complex_number = ComplexNumberWithConstructor(3.0, -4.5)
assert complex_number.real, complex_number.imaginary == (3.0, -4.5)