Eroman: Created page with "= Lecture 7 = Data types == Data type things to know == clases in python describe datatype, and when called, create a new object of that type. `type` returns the..."

2017-10-23T22:14:25Z

Created page with "= Lecture 7 = Data types == Data type things to know == clases in python describe datatype, and when called, create a new object of that type. <code>type</code> returns the..."

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= Lecture 7 =

Data types

== Data type things to know ==

clases in python describe datatype, and when called, create a new object of that type. <code>type</code> returns the datatype <code>isinstance</code> check if object is an instance of the class

<pre>In [3]: class A:
...: pass
...:

In [4]: type(A)
Out[4]: type

In [5]: type(int)
Out[5]: type

In [6]: int(10)
Out[6]: 10

In [7]: float(10)
Out[7]: 10.0

In [8]: isinstance(10, int)
Out[8]: True

In [9]: isinstance(10, float)
Out[9]: False

In [10]: class MyInt(int):
pass
....:

In [11]: a = MyInt(10)

In [12]: a
Out[12]: 10

In [13]: type(a)
Out[13]: __main__.MyInt

In [14]: isinstance(a, int)
Out[14]: True</pre>
== Magic Methods ==

there are prefixed and suffixed with '__', sometimes called 'dunder' for 'double underscore'.

They define specific python functionality.

<pre>class A:
def __init__(self):
pass

def __str__(self):
return 'I am an instance of A'

a = A()
print(a.__str__())
print(str(a))</pre>
=== Task 1 ===

Make an integer which is: equal to both 5, 6 and the actual number (itself) greater than 3 less than 2

=== Solution ===

<source lang="python">from unittest import TestCase

class MyInt(int):
"""Define some magic methods!"""
def __lt__(self, x):
if x == 2:
return True
else:
return super().__lt__(x)

def __gt__(self, x):
if x == 3:
return True
else:
return super().__gt__(x)

def __eq__(self, x):
if x == 5 or x == 6:
return True
else:
return super().__eq__(x)

class MyIntTestCase(TestCase):
def test_gt(self):
a = MyInt(1)
self.assertTrue(a > 3)

def test_lt(self):
a = MyInt(100)
self.assertTrue(a < 2)

def test_eq(self):
a = MyInt(1)
self.assertTrue(a == 5)
self.assertTrue(a == 6)</source>
```

Advanced Python (Fall 2017)/lecture7 - Revision history

Eroman: Created page with "= Lecture 7 = Data types == Data type things to know == clases in python describe datatype, and when called, create a new object of that type. type returns the..."

Eroman: Created page with "= Lecture 7 = Data types == Data type things to know == clases in python describe datatype, and when called, create a new object of that type. `type` returns the..."