Writing an array to a text file is simple:

savetxt(filename,data)

There are two useful parameters given as strings, fmt and delimiter, which control the format and the delimiter between columns. The defaults are space for the delimiter and %.18e for the format, which corresponds to the exponential format with all digits. The formatting parameters are used as follows:

x = range(100) # 100 integers
savetxt('test.txt',x,delimiter=',')   # use comma instead of space
savetxt('test.txt',x,fmt='%d') # integer format instead of float with e

Reading to an array from a text file is done with the help of the following syntax:

filename = 'test.txt'
data = loadtxt(filename)

Due to the fact that each row in an array must have the same length, each row in the text file must have the same number of elements. Similar to savetxt, the default values are float and the delimiter is space. These can be set using the dtype and delimiter parameters. Another useful parameter is comments, which can be used to mark what symbol is used for comments in the data file. An example for using the formatting parameters is as follows:

data = loadtxt('test.txt',delimiter=';')    # data separated by semicolons
data = loadtxt('test.txt',dtype=int,comments='#') # read to integer type, 
                                               #comments in file begin with a hash character