Array of arrays Python NumPy

Question

I am using Python NumPy  and I have two arrays like the following   array1    1 2 3  array2    4 5 6    And I would like to create a new array   array3     1 2 3    4 5 6     and append items to it  So for example if the new items to append are   array4    7 8 9  array5    10 11 12    Then now array3 would be an array with two rows and two columns like the one shown below   array3    1 2 3    4 5 6            7 8 9    10 11 12     I seem to have problems because the elements of my arrays are not separated by commas

User · Answer

If the file is only numerical values separated by tabs, try using the csv library: http://docs.python.org/library/csv.html (you can set the delimiter to '\t')

If you have a textual file in which every line represents a row in a matrix and has integers separated by spaces\tabs, wrapped by a 'arrayname = [...]' syntax, you should do something like:

import re
f = open("your-filename", 'rb')
result_matrix = []
for line in f.readlines():
    match = re.match(r'\s*\w+\s+\=\s+\[(.*?)\]\s*', line)
    if match is None:
        pass # line syntax is wrong - ignore the line
    values_as_strings = match.group(1).split()
    result_matrix.append(map(int, values_as_strings))

User · Answer

It seems strange that you would write arrays without commas  is that a MATLAB syntax    Have you tried going through NumPy s documentation on multi-dimensional arrays   It seems NumPy has a  Python-like  append method to add items to a NumPy n-dimensional array    gt  gt  gt  p   np array   1 2   3 4      gt  gt  gt  p   np append p    5 6    0    gt  gt  gt  p   np append p    7   8   9   1    gt  gt  gt  p array   1  2  7    3  4  8    5  6  9      It has also been answered already     From the documentation for MATLAB users   You could use a matrix constructor which takes a string in the form of a matrix MATLAB literal   mat  1 2 3  4 5 6    or  matrix   1 2 3  4 5 6      Please give it a try and tell me how it goes

User · Answer

You ll have problems creating lists without commas  It shouldn t be too hard to transform your data so that it uses commas as separating character   Once you have commas in there  it s a relatively simple list creation operations   array1    1 2 3  array2    4 5 6   array3    array1  array2   array4    7 8 9  array5    10 11 12   array3    array3   array4  array5     When testing we get   print array3      1  2  3    4  5  6      7  8  9    10  11  12      And if we test with indexing it works correctly reading the matrix as made up of 2 rows and 2 columns   array3 0  1   4  5  6   array3 1  1   10  11  12    Hope that helps

User · Answer

a np array   1 2 3   4 5 6     a tolist    tolist method mentioned above will return the nested Python list

[python] Array of arrays (Python/NumPy)

Examples related to python

Examples related to arrays

Examples related to numpy