That should know about class in Python

__init__ methods are optional, but when you define one, you must remember to explicitly call the ancestor’s __init__ method (if it defines one). This is more generally true: whenever a descendant wants to extend the behavior of the ancestor, the descendant method must explicitly call the ancestor method at the proper time, with the proper arguments.

About lambda

So-called lambda functions can be used anywhere a function is required as in-line function in C++.

def f(x):
return x*2
f(4)

We can replace this function by:
g = lambda x: x*2
g(4)

Same!!!!!!

Python most important functions

1. type
2. str
3. dir

The type Function

• The type function returns the datatype of any arbitrary object.
• type(1) — > <type ‘int’>.

The str Function

• The str coerces data into a string.
• Every datatype can be coerced into a string.
• str(1) — > ’1′.

Introducing dir

• dir returns a list of the attributes and methods of any object: modules, functions, strings, lists, dictionaries… pretty much anything.

Introducing callable

• the callable function takes any object and returns True if the object can be called, or False otherwise.

Two special command.

import __builtin__
dir(__builtin__)

Data type

Python has three native data types:
1. Dictionary.
2. List.
3. Tuples.

Dictionary

• Defining a Dictionary: d = {“server”:”mpilgrim”, “database”:”master”} — you create a new dictionary with two elements and assign it to the variable d. Each element is a key-value pair, and the whole set of elements is enclosed in curly braces
• Dictionary Keys Are Case-Sensitive.
• You mis Datatypes in a Dictionary.

List

• Defining a List : li = ["a", "b", "mpilgrim", "z", "example"] —- you define a list of five elements. Note that they retain their original order. This is not an accident. A list is an ordered set of elements enclosed in square brackets.
• Negative List Indices is possible.
• There many other operation like Slicing a List, Shorthanding etc is possible.

Tuples

• A tuple is an immutable list. A tuple can not be changed in any way once it is created.
• Defining a tuple: t = (“a”, “b”, “mpilgrim”, “z”, “example”) — A tuple is defined in the same way as a list, except that the whole set of elements is enclosed in parentheses instead of square brackets.
• Tuples Have No Methods.
• You can, however, use in to see if an element exists in the tuple.