from complex import Complex
# Creating and instance of Complex class
comp = Complex(3, 4)
# When you're accessing to unexisting attribute it would be created in instant
# locally for this object.
comp.new_attr = 14
print comp.new_attr
# But also you have the power to remove attributes as soon as you thing you don't
# need them. You only need to use `del`syntax for this.
del comp.new_attr
# The error will be rised here, since we have no `new_attr` anymore.
try:
print comp.new_attr
except AttributeError as e:
print "Error: {0}".format(e)
# But also you have the power to remove attributes which were here originaly.
del comp.im
# But that could broke up everything, cause they possibly were used in different
# methods of class. For example take a look on the bottom lines, here problem
# shall appears with calling `__repr__` method.
try:
print comp
except (AttributeError, KeyError) as e:
print "Error: {0}".format(e)
# But you always can restore attributes.
comp.im = 3
print comp
# Class definition for complex number. More details on Complex number is
# here: https://en.wikipedia.org/wiki/Complex_number
class Complex:
"""A complex number is a number that can be expressed in the form a + bi,
where a and b are real numbers and i is the imaginary unit, that satisfies
the equation i**2=-1."""
# The line above called "the doc string" and would appears in all hints and
# __doc__ attribute later.
# This is the instance constructor, place to initialize values of exact
# instance, please do not confuse it with __new__ which is more complicated
# topic of for next level lecture.
def __init__(self, re, im=0):
self.re = re
self.im = im
def __repr__(self):
# Method to create object representation.
return "{re} + {im}i".format(**self.__dict__)
# Following line means that name of this method would be used as name of
# read-only property (to make writable one there additional syntax)
@property
def abs(self):
return (self.re**2 + self.im**2)**0.5
