python - Formatting numpy array and save to a *.txt -

i want formatting numpy array , save in *.txt file

the numpy array looks this:

a = [ 0.1   0.2   0.3   0.4   ... ] , [ 1.1   1.2   1.3   1.4   ... ] , ... 

and output *.txt should looks this:

0   1:0.1   2:0.2   3:0.3   4:0.4   ... 0   1:1.1   2:1.2   3:1.3   1:1.4   ... ... 

don't know how that.

thank you.

well jaba thank you. fixed answer little bit

import numpy np  = np.array([[1,3,5,6], [4,2,4,6], [6,3,2,6]])  ret = ""  in range(a.shape[0]):     ret += "0 "     j in range(a.shape[1]):         ret += " %s:%s" % (j+1,float(a[i,j])) #have space between numbers better reading , think should starts 1 not 0 ?! ret +="\n"  fd = open("output.sparse", "w") fd.write(ret) fd.close() 

do thinks thats ok?!

rather simple:

import numpy np  = np.array([[0.1, 0.2, 0.3, 0.4], [1.1, 1.2, 1.3, 1.4], [2.1, 2.2, 2.3, 2.4]])  open("array.txt", 'w') h:       row in a:         h.write("0")         n, col in enumerate(row):             h.write("\t{0}:{1}".format(n+1, col))  # can change \t (tab) character number of spaces, if that's require         h.write("\n") 

and output:

0       1:0.1   2:0.2   3:0.3   4:0.4 0       1:1.1   2:1.2   3:1.3   4:1.4 0       1:2.1   2:2.2   3:2.3   4:2.4 

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my original example involves lot of disk writes. if array large, can pretty inefficient. number of writes can reduced, though, such as:

with open("array.txt", 'w') h:       row in a:         row_str = "0"         n, col in enumerate(row):             row_str = "\t".join([row_str, "{0}:{1}".format(n+1, col)])         h.write(''.join([row_str, '\n'])) 

you can reduce number of writes further 1 constructing 1 large string , writing @ end, in case in beneficial (i.e. huge array), run memory problems constructing huge string. anyway, it's you.