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

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:

>>> p = np.array([[1,2],[3,4]])

>>> p = np.append(p, [[5,6]], 0)

>>> p = np.append(p, [[7],[8],[9]],1)

>>> 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

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

[python] Array of arrays (Python/NumPy)

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