Python Power

What we'll cover

• Basics
• Language Features
  • Operator Overloading
  • Duck Typing
  • Multiple Inheritance
  • Comprehensions
• PIP
• Popular applications of Python
  • Pandas/numpy
  • Django

The Basics: Numbers

# Dynamic typing means different number types based on syntax

my_num = 1    # integer 
my_num = 1.0  # float (all floats are doubles)
my_num = 1.   # also float!

# Most conversion can be done automatically

>>> 1.1 * 2
2.2

# But some can be tricky

>>> 1/2
0

>>> 1./2
0.5

• All floats are double percision
• In Python3, integers have no defined limit

The Basics: Strings

>>> "Hello world"[0] # iterable!
"H"

>>> "Hello world"[:5] # iterable!
"Hello"

>>> for letter in "yams": # iterable!
...    print letter.upper()
Y
A
M
S

# Most operators work with strings

>>> "wow" * 3
"wowwowwow"

>>> "hello " + "world"
"hello world"

# And unlike JavaScript, things make sense!
>>> "hello" + 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects

The Basics: Functions

The Basics: Objects

Operator Overloading

• Python has many magic methods and names
• Magic methods begin and end with two underscores

  • __init__, __add__, __name__

• We can override magic methods to change behaviour

Operator Overloading

Operator Overloading

Duck Typing

• Duck typing is almost the absence of actual typing
  • Objects are typed based on their attributes
  • If the attributes match, the types match
  • An object is of any type until... it isn't
• Python uses duck typing, but objects still have types

  • You shouldn't care what type of object you have

  • Care if you can do the required action with your object

• If types don't match, a TypeError or AttributeError is raised

Duck Typing

>>> a = [0,1 2, 3]
>>> print a[0]
0
>>> b = {'a': 0, 'b': 1}
>>> print b['a']
0

# Is the same as

>>> a =  [0,1 2, 3]
>>> print list.__getitem__(a, 0)
0
>>> b = {'a': 0, 'b': 1}
>>> print dict._getitem__(b, 'a')
0


# Both lists and dictionaries are supported by this method:
def getit(item, key):
    return item[key]

Multiple Inheritance

Multiple Inheritance

Comprehensions

PIP

• the npm of Python
• dope

Pandas/NumPy

• Math!
• Popular in data science, ML
• Slower than something like C, but not if you include the time it takes to write it
• Loosely types languages are great for data science
• Python's built in number support helps power other libraries
  • Fraction, Decimal types
  • ints with no max size
  • Simple syntax for integer operations

Django

• The most popular Python web framework
• Other include:
  • Flask
  • Twisted
• Highly pragmatic, convention based framework
• Built in admin panel for working with models
• Decent ORM
• Control all database migrations in Python, most autogenerated

thanks yo