How to group data read from a file?

[maximus tee]

hi,

assuming i have a file that contains below data:
cell Bit
0 1
1 X
2 1
3 0
4 X
5 X
6 X
7 X
8 1
9 X
10 0
11 0
12 X
13 X
14 1
15 1

how can i group every 4 bits into a row? for eg:
ROW1=01X1
ROW2=XXXX
ROW3=00X1
ROW4=11XX

i'm using Python 2.5, Win XP.

thanks
maximus

[bvdet]

Here's one way:

Open the file, assigning the object to an identifier. Initialize an empty list to contain the strings representing 4 bits and another list to contain the characters. Iterate on the file object using enumerate, skipping the first line. Append the last character of next four lines to the character list (using the modulo operator to determine when to do this), then join the character list and append it to the 4 bits list and reinitialize the character list. After the end of file is reached, close the file object and convert the list into a formatted string.

It is simpler than it sounds. Give it a shot.

[maximus tee]

thanks. btw, do you have any advice on a better s/w to use to debug python script. i'm only using IDLE and sometimes i get traceback error and not sure how to debug it except to that line.

here's the code:

def main():

    new_rows = {}
    values = []
           
    f=open('test.txt')
    for line in f:
        
        values.append(line.rstrip('\n')[-1])
        

        x = []         
        x += values    

        for count in xrange(len(values)/4):
            temp_values = (x.pop(3))+(x.pop(2))+(x.pop(1))+(x.pop(0))
            new_rows['ROW'+str(count+1)] = temp_values
        print new_rows        

if __name__ == '__main__':
    main()

[maximus tee]

the code seems to give wrong result from what i expect.
result:
{'ROW1': '1X1 ', 'ROW2': 'XXX0', 'ROW3': '0X X', 'ROW4': '1XX0'}

but i'm expecting:
ROW1=01X1
ROW2=XXXX
ROW3=00X1
ROW4=11XX

pls advise. tq

[bvdet]

I modified your function somewhat. Variable values and x contained the same data, so I eliminated x. A dictionary is unordered, so I changed new_rows to another list. I used range with a step of 4 and slicing to get the characters. I also skipped the first line, assuming the first line contains the column labels.

def main():
    new_rows = []
    values = []
    f=open('test.txt')
    f.next()
    for line in f:
        values.append(line.rstrip('\n')[-1])
    f.close()
    for count in xrange(0, len(values), 4):
        new_rows.append(('ROW'+str((count/4)+1),values[count:count+4]))
    print "\n".join(["%s=%s" % (item[0], "".join(item[1])) for item in new_rows])
    
 
if __name__ == '__main__':
    main()

Here's the way I was suggesting:

f = open("test.txt")
f.next()
dataList = []
strList = []
for i, line in enumerate(f):
    strList.append(line.strip().split()[1])
    if not (i+1)%4:
        dataList.append("".join(strList))
        strList = []
f.close()
output = "\n".join(["ROW%s=%s" % (i+1, dataList[i]) for i in range(len(dataList))])
print output

[bvdet]

For a Python editor, I prefer Pythonwin over Idle. There are several other good editors out there.

[maximus tee]

sorry i didnt mention that i'm using Python 2.5 and Win XP. would like to check whether next() work for Python 2.5, i thought i read it somewhere it doesnt. anyway, i tried the code, it didnt complain any error. so i guess it works on Python 2.5 too..
i have a more complex data file as attached and i modified the code to be:

f = open("test2.txt") 
f.next() 
dataList = [] 
strList = [] 
for i, line in enumerate(f): 
    strList.append(line.strip().split()[-1]) 
    if not (i+1)%128: 
        dataList.append("".join(strList)) 
        strList = [] 
f.close() 
output = "\n".join(["ROW%s=%s" % (i+1, dataList[i]) for i in range(len(dataList))]) 
print output

and it seems to be working too. :)

[bvdet]

File object method readline() could be substituted for next(). If you don't have labels on the first line in the data file, leave out f.next().

[maximus tee]

i notice the code extracts until 128x4=512. there are 8 characters being truncated. total there are 520. how do i resolve this? tq

[bvdet]

strList will contain data. Test for this condition and add to output as needed.

[maximus tee]

thanks for your advice. :)