Structured data, Python Programming

Structured data

We will often  want  to work  with  large  groups of data.   Rather  than  providing  each  number its own  value,  we need  to manage the data  into natural structures: grocery  lists, matrices, groups of employee medical records. We will explain  a simple  but  enormously useful  and ?exible list, which is conveniently create into Python: the list. The precise information  of how lists are shown inside a computer vary from language to language. We will take an abstract model  in which we think of a list as an ordered sequence of memory locations that numbers. So, for example, in Python, we may show a list of three integers as:

 

644_structured data.png

 

 

Now that we have lists, we have some new kinds  of statements, which let us extract elements of a list by specifying their indices.   An index  of 0 related to the ?rst  element of a list.  An index  of -1 related to the last element So, if a is bound as above, then we would have:

 

>>> a[0]

>>> a[2] 

>>> a[-1] 

>>> a[3] 

 

Traceback (most recent call last): File "", line 1, in IndexError: list index out of range.Note that if we attempt to access an element of the list that is not present, then a exception is generated.

 

 

847_structured data  2.png

 

 

It is also possible  to have  an empty list, which  is given in Python as []. We will show it in our memory diagrams as a short box. So example, this list  looks like this in memory:

>>> z = [3, [], [[]]]

 

 

 

515_structured data  3.png

 

Python has a useful method, len, which takes a list as an argument and gives its size. It does not look inside  the elements of the list-it just returns the number of elements at the top level of list. So, we take

 

>>> len([1, 2, 3])

3

>>> len([[1, 2, 3]])

1

 

Posted Date: 8/11/2012 1:38:38 AM | Location : United States







Related Discussions:- Structured data, Assignment Help, Ask Question on Structured data, Get Answer, Expert's Help, Structured data Discussions

Write discussion on Structured data
Your posts are moderated
Related Questions
Assume you have a truck which has to travel across a desert from the base camp at position 0 (left) to the target camp at position 4 (right). The intermediate positions 1,2, and 3

#Why can''t I cd my Desktop? A minute ago I would open up cmd and it starts in C:\Users\myname but now it''s starting in C:\WINDOWS\system> and I don''t where I am or how to get ou


protocol rdt2.2 considers there is a bit errors between sender to receiver and also from receiver to sender. So now we have to consider checking bit errors introduced in reply from

Write a program that requests a password after the author/program information is displayed. Make the password "hello". The program should then ask the user for their name: if the n

what are the issues assciated with top-down analysis

Synthetic models One  goal  of various  people in a variety of sub-disciplines of  electrical  engineering and  computer science is automatic synthesis of machine from  formal

Every programming language has to have  some method for indicating grouping of operations. Here is how you execute an if-then-else structure in Java:   if (s == 1){ s = s

What if you had a list of integer values, and you need to add  them  up and give the sum?  Here are a number of different types of doing  it. First,  here  is a type in a style

Non-local references So far, whenever we needed to compute a variable, there  was  a binding for that  variable in the 'local' environment (the environment in which  we were e