Reading-notes
Dunder Methods
They are easy to recognize because they start and end with double underscores, for example __init__ or __str__.
sometimes called magic methods.
1-Object Initialization: __init__
construct account objects from the Account class I need a constructor (setting up the object)
class Account:
"""A simple account class"""
def __init__(self, owner, amount=0):
"""
This is the constructor that lets us create
objects from this class
"""
self.owner = owner
self.amount = amount
self._transactions = []
Object Representation: __str__, __repr__
provide a string representation of your object for the consumer of your class
- repr: The “official” string representation of an object
- str: The “informal” or nicely printable string representation of an object.
Iteration: __len__, __getitem__, __reversed__
to iterate over our account object
def __len__(self):
return len(self._transactions)
def __getitem__(self, position):
return self._transactions[position]
To iterate over transactions in reversed order you can implement the reversed special method:
def __reversed__(self):
return self[::-1]
Operator Overloading for Comparing : __eq__, __lt__
to compare Python objects
from functools import total_ordering
@total_ordering
class Account:
# ... (see above)
def __eq__(self, other):
return self.balance == other.balance
def __lt__(self, other):
return self.balance < other.balance
Operator Overloading for Merging __add__
def __add__(self, other):
owner = '{}&{}'.format(self.owner, other.owner)
start_amount = self.amount + other.amount
acc = Account(owner, start_amount)
for t in list(self) + list(other):
acc.add_transaction(t)
return acc
Callable Python Objects: __call__
make an object callable like a regular function
def __call__(self):
print('Start amount: {}'.format(self.amount))
print('Transactions: ')
for transaction in self:
print(transaction)
print('\nBalance: {}'.format(self.balance))
to call it
acc()
Context Manager Support and the With Statement: __enter__, __exit__
probability and statistics
probability
What is the chance of an event happening,event is some outcome of interest
the high point in a normal distribution represents the event with the highest probability of occurring. As you get farther away from this event on either side, the probability drops rapidly, forming that familiar bell-shape.
statistics
The high point in a statistical context actually represents the mean. As in probability, as you get farther from the mean, you rapidly drop off in frequency. That is to say, extremely high and low deviations from the mean are present but exceedingly rare.
Central Limit Theorem
Central Limit Theorem dictates that the distribution of these estimates will look like a normal distribution
### Three Sigma Rule The arithmetic mean is the simplest and most widely used measure of a mean, or average.
Z-score
A Z-score is a numerical measurement that describes a value’s relationship to the mean of a group of values. Z-score is measured in terms of standard deviations from the mean.
