Create 3D array using Python

Question

I would like to create a 3D array in Python  2 7  to use like this  distance i  j  k   And the sizes of the array should be the size of a variable I have   nnn  I tried using  distance        n  n   but that didn t seem to work  I can only use the default libraries  and the method of multiplying  i e    0  n  n  wont work because they are linked to the same pointer and I need all of the values to be individual

User · Answer

You can also use a nested for loop like shown below  n   3 arr      for x in range n       arr append         for y in range n           arr x  append             for z in range n               arr x  y  append 0  print arr

User · Answer

The right way would be     0 for   in range n   for   in range n   for   in range n      What you re trying to do should be written like  for NxNxN      0  n  n  n   but that is not correct  see  Adaman comment why

User · Answer

If you insist on everything initializing as empty  you need an extra set of brackets on the inside       instead of     since this is  a list containing 1 empty list to be duplicated  as opposed to  a list containing nothing to duplicate     distance        n  n  n

User · Answer

You should use a list comprehension    gt  gt  gt  import pprint  gt  gt  gt  n   3  gt  gt  gt  distance      0 for k in xrange n   for j in xrange n   for i in xrange n    gt  gt  gt  pprint pprint distance     0  0  0    0  0  0    0  0  0       0  0  0    0  0  0    0  0  0       0  0  0    0  0  0    0  0  0     gt  gt  gt  distance 0  1   0  0  0   gt  gt  gt  distance 0  1  2  0   You could have produced a data structure with a statement that looked like the one you tried  but it would have had side effects since the inner lists are copy-by-reference    gt  gt  gt  distance    0  n  n  n  gt  gt  gt  pprint pprint distance     0  0  0    0  0  0    0  0  0       0  0  0    0  0  0    0  0  0       0  0  0    0  0  0    0  0  0     gt  gt  gt  distance 0  0  0    1  gt  gt  gt  pprint pprint distance     1  0  0    1  0  0    1  0  0       1  0  0    1  0  0    1  0  0       1  0  0    1  0  0    1  0  0

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d3      0 for col in range 4  for row in range 4   for x in range 6    d3 1  2  1     144  d3 4  3  0     3 12  for x in range len d3        print d3 x       0  0  0  0    0  0  0  0    0  0  0  0    0  0  0  0     0  0  0  0    0  0  0  0    0  144  0  0    0  0  0  0     0  0  0  0    0  0  0  0    0  0  0  0    0  0  0  0     0  0  0  0    0  0  0  0    0  0  0  0    0  0  0  0     0  0  0  0    0  0  0  0    0  0  0  0    3 12  0  0  0     0  0  0  0    0  0  0  0    0  0  0  0    0  0  0  0

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Create 3D array for given dimensions -  x  y  z    author  Naimish Agarwal       def three d array value   dim               Create 3D-array      param dim  a tuple of dimensions -  x  y  z       param value  value with which 3D-array is to be filled      return  3D-array              return    value for   in xrange dim 2    for   in xrange dim 1    for   in xrange dim 0     if   name         main         array   three d array False    2  3  1       x   len array      y   len array 0       z   len array 0  0       print x  y  z      array 0  0  0    True     array 1  1  0    True      print array   Prefer to use numpy ndarray for multi-dimensional arrays

User · Answer

There are many ways to address your problem   First one as accepted answer by  robert  Here is the generalised solution for it   def multi dimensional list value   args      args dimensions as many you like  EG    args   4 3 2   gt  x 4  y 3  z 2     value can only be of immutable type  So  don t pass a list here  Acceptable value   0  -1   X   etc    if len args   gt  1      return   multi dimensional list value   args 1    for col in range args 0      elif len args     1   base case of recursion     return   value for col in range args 0      else   edge case when no values of dimensions is specified      return None  Eg   gt  gt  gt  multi dimensional list -1  3  4    2D list   -1  -1  -1  -1    -1  -1  -1  -1    -1  -1  -1  -1    gt  gt  gt  multi dimensional list -1  4  3  2    3D list    -1  -1    -1  -1    -1  -1      -1  -1    -1  -1    -1  -1      -1  -1    -1  -1    -1  -1      -1  -1    -1  -1    -1  -1     gt  gt  gt  multi dimensional list -1  2  3  2  2     4D list     -1  -1    -1  -1      -1  -1    -1  -1      -1  -1    -1  -1        -1  -1    -1  -1      -1  -1    -1  -1      -1  -1    -1  -1      P S If you are keen to do validation for correct values for args i e  only natural numbers  then you can write a wrapper function before calling this function   Secondly  any multidimensional dimensional array can be written as single dimension array  This means you don t need a multidimensional array  Here are the function for indexes conversion   def convert single to multi value  max dim     dim count   len max dim    values    0  dim count   for i in range dim count-1  -1  -1    reverse iteration     values i    value max dim i      value    max dim i    return values   def convert multi to single values  max dim     dim count   len max dim    value   0   length of dimension   1   for i in range dim count-1  -1  -1    reverse iteration     value    values i  length of dimension     length of dimension    max dim i    return value  Since  these functions are inverse of each other  here is the output   gt  gt  gt  convert single to multi convert multi to single  1 4 6 7   23 45 32 14    23 45 32 14    1  4  6  7   gt  gt  gt  convert multi to single convert single to multi 21343  23 45 32 14    23 45 32 14   21343   If you are concerned about performance issues then you can use some libraries like pandas  numpy  etc

User · Answer

numpy arrays are designed just for this case    numpy zeros  i j k     will give you an array of dimensions ijk  filled with zeroes   depending what you need it for  numpy may be the right library for your needs

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def n arr n  default 0  size 1       if n is 0          return default      return  n arr n-1  default  size  for   in range size    arr   n arr 3  42  3  assert arr 2  2  2   42

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