[Tutor] Please Help

Fri Mar 22 08:48:39 CET 2013

Hi Arijit,
I have modified your program a bit and it is working fine for me. Values greater than 5 are being printed. Here is the code:
f = open ("D:\\digi_2.txt", "r+") lines = f.readlines() number_list = [] for line in lines:     	print line	for number in line.split(','): 		#number_list.append(float(number)) 		number_list.append(int(number)) 
s_data = [] for i in number_list:	print i	#if number_list[i] > 5: 	if(i>5):		s_data.append(i)
for x in s_data:	print 'Data val:', float(x) 

RegardsSuhas
To: tutor at python.org
From: arijit.ukil at tcs.com
Date: Fri, 22 Mar 2013 12:54:01 +0530
Subject: [Tutor] Please Help

Hi,

I have another small problem. Pls help.

I have written the following code:

f = open ("digi_2.txt", "r+")

lines = f.readlines()

for line in lines:

    number_list = []

    for number in line.split(','):

        number_list.append(float(number))

s_data = []

for i in range(len(number_list)):

    if number_list[i] >
5:

        s_data =
number_list[i]

print 'Data val:', s_data

The problem is: it is printing only
the last value, not all the values. In this case '10', not
'9,8,6,10'.

Regards,

Arijit Ukil

Tata Consultancy Services

Mailto: arijit.ukil at tcs.com

Website: http://www.tcs.com

____________________________________________

Experience certainty.        IT Services

       Business Solutions

       Outsourcing

____________________________________________

From:
Amit Saha <amitsaha.in at gmail.com>

To:
Arijit Ukil <arijit.ukil at tcs.com>

Cc:
tutor at python.org

Date:
03/21/2013 05:30 PM

Subject:
Re: [Tutor] Please Help

Hi Arijit,

On Thu, Mar 21, 2013 at 8:42 PM, Arijit Ukil <arijit.ukil at tcs.com>
wrote:

>

> I am new to python. I like to calculate average of the numbers by
reading

> the file 'digi_2.txt'. I have written the following code:

>

> def average(s): return sum(s) * 1.0 / len(s)

>

> f = open ("digi_2.txt", "r+")

>

> list_of_lists1 = f.readlines()

>

>

> for index in range(len(list_of_lists1)):

>

>

>     tt = list_of_lists1[index]

>

>     print 'Current value :', tt

>

> avg =average (tt)

>

>

> This gives an error:

>

> def average(s): return sum(s) * 1.0 / len(s)

> TypeError: unsupported operand type(s) for +: 'int' and 'str'

>

> I also attach the file i am reading.

>

>

>

> Please help to rectify.

The main issue here is that when you are reading from a file, to

Python, its all strings. And although, 'abc' + 'def' is valid, 'abc' +

5 isn't (for example). Hence, besides the fact that your average

calculation is not right, you will have to 'convert' the string to an

integer/float to do any arithmetic operation on them. (If you know C,

this is similar to typecasting). So, coming back to your program, I

will first demonstrate you a few things and then you can write the

program yourself.

If you were to break down this program into simple steps, they would be:

1. Read the lines from a file (Assume a generic case, where you have

more than one line in the file, and you have to calculate the average

for each such row)

2. Create a list of floating point numbers for each of those lines

3. And call your average function on each of these lists

You could of course do 2 & 3 together, so you create the list and call

the average function.

So, here is step 1:

with open('digi.txt','r') as f:

    lines = f.readlines()

Please refer to

http://docs.python.org/2/tutorial/inputoutput.html#methods-of-file-objects

for an explanation of the advantage of using 'with'.

Now, you have *all* the lines of the file in 'lines'. Now, you want to

perform step 2 for each line in this file. Here you go:

for line in lines:

    number_list = []

    for number in line.split(','):

        number_list.append(float(number))

 (To learn more about Python lists, see

http://effbot.org/zone/python-list.htm).
It is certainly possible to

use the index of an element to access elements from a list, but this

is more Pythonic way of doing it. To understand this better, in the

variable 'line', you will have a list of numbers on a single line. For

example: 1350696461, 448.0, 538660.0, 1350696466, 448.0. Note how they

are separated by a ',' ? To get each element, we use the split( )

function, which returns a list of the individual numbers. (See:

http://docs.python.org/2/library/stdtypes.html#str.split).
And then,

we use the .append() method to create the list. Now, you have a

number_list which is a list of floating point numbers for each line.

Now, step 2 & 3 combined:

for line in lines:

    number_list = []

    for number in line.split(','):

        number_list.append(float(number))

    print average(number_list)

Where average( ) is defined as:

def average(num_list):

    return sum(num_list)/len(num_list)

There may be a number of unknown things I may have talked about, but i

hope the links will help you learn more and write your program now.

Good Luck.

-Amit.

--

http://amitsaha.github.com/

=====-----=====-----=====

Notice: The information contained in this e-mail

message and/or attachments to it may contain 

confidential or privileged information. If you are 

not the intended recipient, any dissemination, use, 

review, distribution, printing or copying of the 

information contained in this e-mail message 

and/or attachments to it are strictly prohibited. If 

you have received this communication in error, 

please notify us by reply e-mail or telephone and 

immediately and permanently delete the message 

and any attachments. Thank you

_______________________________________________
Tutor maillist  -  Tutor at python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/tutor/attachments/20130322/eff86fe3/attachment.html>