Mailing List Archive: Python: Python

query regarding file handling.

Index | Next | Previous | View Threaded

ankita.dutta09 at gmail

Nov 12, 2009, 1:59 AM

Post #1 of 4 (394 views)
Permalink

query regarding file handling.

hi all,

i have a file of 3x3 matrix of decimal numbers(tab separated). like this :

0.02 0.38 0.01
0.04 0.32 0.00
0.03 0.40 0.02

now i want to read 1 row and get the sum of a particular row. but when i am
trying with the following code, i am getting errors :

*code*:
"
ln1=open("A.txt","r+") # file "A.txt" contains my matrix
lines1=ln1.readlines()
n_1=[ ]

for p1 in range (0,len(lines1)):
f1=lines1[p1]
n_1.append((f1) )
print n_1
print sum(n_1[0])

"

*output*:

['0.0200\t0.3877\t0.0011\n', '0.0040\t0.3292\t0.0001\n',
'0.0355\t0.4098\t0.0028\n', '0.0035\t0.3063\t0.0001\n',
'0.0080\t0.3397\t0.0002\n']

Traceback (most recent call last):
File "A_1.py", line 20, in <module>
print sum(nodes_1[0])
File "/usr/lib/python2.5/site-packages/numpy/core/fromnumeric.py", line
993, in sum
return _wrapit(a, 'sum', axis, dtype, out)
File "/usr/lib/python2.5/site-packages/numpy/core/fromnumeric.py", line
37, in _wrapit
result = getattr(asarray(obj),method)(*args, **kwds)
TypeError: cannot perform reduce with flexible type

* what I think:*

as the list is in form of '0.0200\t0.3877\t0.0011\n' , n_1[0] takes
it as a whole string which includes "\t" , i think thats why they are
giving error.

now how can i read only required numbers from this line
'0.0200\t0.3877\t0.0011\n' and find their sum ?
can you kindly help me out how to properly code thing .

thank you,

regards

clp2 at rebertia

Nov 12, 2009, 2:15 AM

Post #2 of 4 (377 views)
Permalink

Re: query regarding file handling. [In reply to]

On Thu, Nov 12, 2009 at 1:59 AM, ankita dutta <ankita.dutta09 [at] gmail> wrote:
> hi all,
>
> i have a file of 3x3 matrix of decimal numbers(tab separated). like this :
>
> 0.02    0.38    0.01
> 0.04    0.32    0.00
> 0.03    0.40    0.02
>
> now i want to read 1 row and get the sum of a particular row. but when i am
> trying with the following code, i am getting errors :

Try using the `csv` module, which despite its name, works on the
tab-delimited variant of the format as well:
http://docs.python.org/library/csv.html

Cheers,
Chris
--
http://blog.rebertia.com
--
http://mail.python.org/mailman/listinfo/python-list

himanshu.garg at gmail

Nov 12, 2009, 4:16 AM

Post #3 of 4 (372 views)
Permalink

Re: query regarding file handling. [In reply to]

2009/11/12 ankita dutta <ankita.dutta09 [at] gmail>:
> hi all,
>
> i have a file of 3x3 matrix of decimal numbers(tab separated). like this :
>
> 0.02    0.38    0.01
> 0.04    0.32    0.00
> 0.03    0.40    0.02
>
> now i want to read 1 row and get the sum of a particular row. but when i am
> trying with the following code, i am getting errors :
>
> code:
> "
> ln1=open("A.txt","r+")    # file "A.txt" contains my matrix
> lines1=ln1.readlines()
> n_1=[ ]
>
> for p1 in range (0,len(lines1)):
>     f1=lines1[p1]
>     n_1.append((f1) )
> print n_1
> print sum(n_1[0])
>
> "
>
> output:
>
> ['0.0200\t0.3877\t0.0011\n', '0.0040\t0.3292\t0.0001\n',
> '0.0355\t0.4098\t0.0028\n', '0.0035\t0.3063\t0.0001\n',
> '0.0080\t0.3397\t0.0002\n']
>
> Traceback (most recent call last):
> File "A_1.py", line 20, in <module>
>     print sum(nodes_1[0])
> File "/usr/lib/python2.5/site-packages/numpy/core/fromnumeric.py", line
> 993, in sum
>     return _wrapit(a, 'sum', axis, dtype, out)
> File "/usr/lib/python2.5/site-packages/numpy/core/fromnumeric.py", line
> 37, in _wrapit
>     result = getattr(asarray(obj),method)(*args, **kwds)
> TypeError: cannot perform reduce with flexible type
>
>
> what I think:
>
> as the list is in form of   '0.0200\t0.3877\t0.0011\n'    , n_1[0] takes
> it as a whole string   which includes "\t" , i think thats why they are
> giving error.
>
> now how can i read only required numbers from this line
> '0.0200\t0.3877\t0.0011\n' and find their sum ?
> can you kindly help me out how to properly code thing .
>

Yes you have it right. Split the string at spaces and convert the
numeric parts to floats before summing. Something along these lines :-

1 ln1=open("A.txt","r+") # file "A.txt" contains my matrix
2 lines1=ln1.readlines()
3 n_1=[ ]
4
5 for p1 in range (0,len(lines1)):
6 f1=lines1[p1]
7 n_1.append((f1) )
8 print n_1
9 import re
10 nos = []
11 for s in re.split('\s+', n_1[0]):
12 if s != '':
13 nos.append(float(s))
14 print nos
15 print sum(nos)

Better still use the csv module as suggested.

Thank You,
++imanshu
--
http://mail.python.org/mailman/listinfo/python-list

rhodri at wildebst

Nov 13, 2009, 6:11 PM

Post #4 of 4 (360 views)
Permalink

Re: query regarding file handling. [In reply to]

On Thu, 12 Nov 2009 09:59:40 -0000, ankita dutta
<ankita.dutta09 [at] gmail> wrote:

> hi all,
>
> i have a file of 3x3 matrix of decimal numbers(tab separated). like this
> :
>
> 0.02 0.38 0.01
> 0.04 0.32 0.00
> 0.03 0.40 0.02
>
> now i want to read 1 row and get the sum of a particular row. but when i
> am
> trying with the following code, i am getting errors :
>
> *code*:
> "
> ln1=open("A.txt","r+") # file "A.txt" contains my matrix
> lines1=ln1.readlines()

You can iterate through the file line by line, so there's no need to read
the whole thing in one go like this.

> n_1=[ ]
>
> for p1 in range (0,len(lines1)):
> f1=lines1[p1]

If you ever write range(len(some_list)) in a 'for' statement, you're
almost certainly making life harder for yourself than you need to. Since
all you use 'pl' for is pulling out the 'current' line, you might as well
just iterate through the list, i.e. replace those two lines with this:

for fl in lines1:

Better, as I mentioned earlier you can skip the whole business of slurping
the file in using 'readlines' and read it one line at a time:

for fl in ln1:

> n_1.append((f1) )
> print n_1
> print sum(n_1[0])
>
[snip]

> * what I think:*
>
> as the list is in form of '0.0200\t0.3877\t0.0011\n' , n_1[0]
> takes
> it as a whole string which includes "\t" , i think thats why they are
> giving error.

You think right.

> now how can i read only required numbers from this line
> '0.0200\t0.3877\t0.0011\n' and find their sum ?
> can you kindly help me out how to properly code thing .

Read the line (as before), then split it on whitespace (the tabs in this
case), and then sum the resulting list. Or as Chris said, get the 'csv'
module to do the hard work for you.

--
Rhodri James *-* Wildebeest Herder to the Masses
--
http://mail.python.org/mailman/listinfo/python-list

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact Gossamer Threads