List of Python Commands

Comments

In a Python command, Comments start with the hash character "#" and it is extended to the end. A commnet may not appear within the string literal.


For example: 
print " Hello world " # this is the first comment 
Hello World is not a Commment as it is inside the quotes.

Comments are not the part of command, but rather intended as documentation for anyone reading the code.

Multiline comments are also possible, and are enclosed by triple double-quote symbols:

""" This is an example of a Multiline Comment 
that goes on 
and on 
and on ."" "

Numbers and Various other data types

Python recognizes several different types of data. For instance, 29 and −65 are integers, while 7.0 and −23.09 are floats or floating point numbers. The type float is (roughly) the same as a real number in mathematics. The number 12345678901 is a long integer ; Python prints it with an “L” appended to the end. Usually the type of a piece of data is determined implicitly.

The Type Function

To see the type of some data, use Python’s built-in type function:


>>> type ( -65) 
< type ’ int ’ >
 >>> type (7.0)
 < type ’ float ’> 
>>> type (12345678901) 
< type ’ long ’> 

Another useful data type is complex, used for complex numbers.


For example: 
>>> 2j 
2j 
>>> 2j -1 
( -1+2 j ) 
>>> complex (2 ,3)
(2+3 j) 
>>> type ( -1+2 j) 
< type ’ complex ’> 

Notice that Python uses j for the complex unit (such that j2= −1) just as physicists do, instead of the letter i preferred by mathematicians.

				

Create Different Types of Lists:

# empty list mylist = [ ] # list of numbers mylist = [2, 3, 4, 5] #list with mixed datatypes mylist = [2, “dzone”, 4.5] # nested list mylist = [“dzone”, [4, 6, 8], ['c']]

Strings

Other useful data types are strings (short for “character strings”); for example "Hello World!".
Strings are sequences of characters enclosed in single or double quotes:


>>> " This is a string " 
’ This is a string ’ 
>>> ’ This is a string , too ’
 ’ This is a string , too ’
 >>> type ( " This is a string ")
 < type ’ str ’ >