text file format from array

Question

Hi,

I have no: of arrays, and i like to take it to text file in specific format, for eg.,

'present form'

a= [1 2 3 4 5 ]

b= [ 1 2 3 4 5 6 7 8 ]  

c= [ 8 9 10 12 23 43 45 56 76 78]

d= [ 1 2 3 4 5 6 7 8 45 56 76 78 12 23 43 ]

The 'required format' in a txt file,

   a   '\t'    b      '\t'     d  '\t'    c

   1   '\t'    1  

   2    '\t'   2  

   3    '\t'   3  

   4    '\t'   4  

   5   '\t'    5  

      6   

      7              

      8

'\t'- 1 tab space

problem is,

I have the array in linear form[a],[b],[c],and d, i have to transpose('required format') and sort [a],[b],[d],and [c] and write it as a txt file

Answer 1

from __future__ import with_statement
import csv
import itertools



a= [1, 2, 3, 4, 5]
b= [1, 2, 3, 4, 5, 6, 7, 8]
c= [8, 9, 10, 12, 23, 43, 45, 56, 76, 78]
d= [1, 2, 3, 4, 5, 6, 7, 8, 45, 56, 76, 78, 12, 23, 43]

with open('destination.txt', 'w') as f:
    cf = csv.writer(f, delimiter='\t')
    cf.writerow(['a', 'b', 'd', 'c']) # header  
    cf.writerows(itertools.izip_longest(a, b, d, c))

Results on destination.txt (<tab>s are in fact real tabs on the file):

a<tab>b<tab>d<tab>c
1<tab>1<tab>1<tab>8
2<tab>2<tab>2<tab>9
3<tab>3<tab>3<tab>10
4<tab>4<tab>4<tab>12
5<tab>5<tab>5<tab>23
<tab>6<tab>6<tab>43
<tab>7<tab>7<tab>45
<tab>8<tab>8<tab>56
<tab><tab>45<tab>76
<tab><tab>56<tab>78
<tab><tab>76<tab>
<tab><tab>78<tab>
<tab><tab>12<tab>
<tab><tab>23<tab>
<tab><tab>43<tab>

Here's the izip_longest function, if you have python < 2.6:

def izip_longest(*iterables, fillvalue=None):
    def sentinel(counter=([fillvalue]*(len(iterables)-1)).pop):
        yield counter()
    fillers = itertools.repeat(fillvalue)
    iters = [itertools.chain(it, sentinel(), fillers) 
             for it in iterables]
    try:
        for tup in itertools.izip(*iters):
            yield tup
    except IndexError:
        pass

Answer 2

Have a look at matplotlib.mlab.rec2csv and csv2rec:

>>> from matplotlib.mlab import rec2csv,csv2rec
# note: these are also imported automatically when you do ipython -pylab

>>> rec = csv2rec('csv file.csv')
>>> rec2csv(rec, 'copy csv file', delimiter='\t')

Answer 3

Just for fun with no imports:

a= [1, 2, 3, 4, 5]
b= [1, 2, 3, 4, 5, 6, 7, 8]
c= [8, 9, 10, 12, 23, 43, 45, 56, 76, 78]
d= [1, 2, 3, 4, 5, 6, 7, 8, 45, 56, 76, 78, 12, 23, 43]

fh = open("out.txt","w")

# header line
fh.write("a\tb\td\tc\n")
# rest of file
for i in map(lambda *row: [elem or "" for elem in row], *[a,b,d,c]):
  fh.write("\t".join(map(str,i))+"\n")

fh.close()

Answer 4

Thank you for your answers, but i face this problem while executing,

with open('destination.txt', 'w') as f:

'with' will become a reserved keyword in Python 2.6

with open('/home/abc/W/array/destination.txt', 'w') as txt : ^
SyntaxError: invalid syntax