Iteration over lists, Python Programming

 

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  you  may  have  learned to write  in a Java class (actually, you would have used  for, but Python does not have a for that works  like the one in C and Java).

 

def addList1(l):

sum  = 0

listLength = len(l)

i =  0

while (i < listLength):

sum  = sum + l[i]

i =  i + 1 return sum

 

It increments the index i from 0 through the length of the list - 1, and includes the appropriate components of the list into the sum.  This is perfectly right, but pretty verbose and easy to get wrong.

Here is a method of version using  Python's for loop.

 

def addList2(l):

sum  = 0

for i in range(len(l)):

sum  = sum + l[i]

return sum

 

A loop of the form

 

for x in l: something will be executed once for each element in the structure l, with the variable x having each successive element in l on each iteration. So,for  x in range(3): print x will print  0 1 2. Back to addList2,  we look that i will take on variables  from 0 to the length  of the list minus 1, and on every iteration, it will include the appropriate component from l into the addition.  This is more compact and simpler to get right than  the ?rst method of version, but still not the good one  we can do!

 

This one is even more direct.

 

def addList3(l):

sum  = 0

for  v in l:

sum  = sum + v return sum

 

We do not ever really need to work with the indices.  Here, the internal variable v gets on each successive integer  in l, and those values  are goes into sum.

 

For the truly  lazy, it turns out that  the function we need  is already built  into Python. It is known as sum:

 

def addList4(l):

return sum(l)

 

Posted Date: 8/9/2012 7:20:38 AM | Location : United States







Related Discussions:- Iteration over lists, Assignment Help, Ask Question on Iteration over lists, Get Answer, Expert's Help, Iteration over lists Discussions

Write discussion on Iteration over lists
Your posts are moderated
Related Questions
Write a program on python to give solution for driven and damped rlc circuit

simple program using list

Your assignment for the semester will involve the development of a system for drawing trees using the Python programming language and the turtle graphics module (turtle.py). Comple

Displaying random geometric graphs in an uniform square, unit disk, dense rim unit disk, and uniform sphere

We encourage you to adopt an interactive style of debugging and programming. Use the Python shell a lot. Write short pieces of code and check them.  It is much  simpler to test the

from urllib2 import urlopen # Open http://placekitten.com/ for reading on line 4! response = kittens.read() body = response[559:1000] # Add your ''print'' statement here!

#que Write a program that will take price data for stocks and print it graphically to the screen. Your program should begin by asking the user for the file name. It should then cre

1 Low Level Exploits 1.1 Savegames Jimmy is becoming increasingly frustrated at the computer game hes playing. He has a save right before the levels boss but he needs either more

Internal models As we want to create  more and more complex  machine with  software programs as controllers, we search  that  it is often needful  to create  additional types

Task This problem creates a list containing names. The list of names will be printed, sorted, printed again in the new sorted order, written to a new output file, and searched. Ca