Two dimensional array in python

Question

I want to know how to declare a two dimensional array in Python   arr         arr 0  append  aa1   arr 0  append  aa2   arr 1  append  bb1   arr 1  append  bb2   arr 1  append  bb3     The first two assignments work fine  But when I try to do  arr 1  append  bb1    I get the following error   IndexError  list index out of range    Am I doing anything silly in trying to declare the 2-D array   Edit  but I do not know the number of elements in the array  both rows and columns

User · Answer

You try to append to second element in array  but it does not exist  Create it   arr         arr 0  append  aa1   arr 0  append  aa2   arr append     arr 1  append  bb1   arr 1  append  bb2   arr 1  append  bb3

User · Answer

the above method did not work for me for a for loop  where I wanted to transfer data from a 2D array to a new array under an if the condition  This method would work a 2d list     1  2    3  4   a 2d list append  5  6   print a 2d list   OUTPUT -   1  2    3  4    5  6

User · Answer

You can first append elements to the initialized array and then for convenience  you can convert it into a numpy array   import numpy as np a        declare null array a append   aa1      append elements a append   aa2    a append   aa3    print a  a np   np asarray a    convert to numpy array print a np

User · Answer

In my case I had to do this  for index  user in enumerate users       table body append         table body index  append user user id      table body index  append user user username   Output    1   john     2   bill

User · Answer

You do not  declare  arrays or anything else in python  You simply assign to a  new  variable  If you want a multidimensional array  simply add a new array as an array element   arr      arr append     arr 0  append  aa1   arr 0  append  aa2     or  arr      arr append   aa1    aa2

User · Answer

When constructing multi-dimensional lists in Python I usually use something similar to ThiefMaster s solution  but rather than appending items to index 0  then appending items to index 1  etc   I always use index -1 which is automatically the index of the last item in the array   i e   arr       arr append     arr -1  append  aa1   arr -1  append  aa2    arr append     arr -1  append  bb1   arr -1  append  bb2   arr -1  append  bb3     will produce the 2D-array  actually a list of lists  you re after

User · Answer

For compititve programming  1  For input the value in an 2D-Array  row input   main list    for i in range 0 row       temp list map int raw input   split           main list append temp list    2  For displaying 2D Array  for i in range 0 row       for j in range 0 len main list 0            print main list i  j           print

User · Answer

We can create multidimensional array dynamically as follows   Create 2 variables to read x and y from standard input    print  Enter the value of x      x int input      print  Enter the value of y      y int input      Create an array of list with initial values filled with 0 or anything using the following code  z   0 for row in range 0 x   for col in range 0 y     creates number of rows and columns for your array data   Read data from standard input   for i in range x            for j in range y                z i  j  input     Display the Result   for i in range x            for j in range y                print z i  j  end               print   n     or use another way to display above dynamically created array is   for row in z       print row

User · Answer

x 3 rows y 3 columns a    create an empty list first for i in range x       a append  0  y  And again append empty lists to original list     for j in range y            a i  j  input  Enter the value

User · Answer

a       for index in range 1  n

User · Answer

There aren t multidimensional arrays as such in Python  what you have is a list containing other lists    gt  gt  gt  arr         gt  gt  gt  len arr  1   What you have done is declare a list containing a single list   So arr 0  contains a list but arr 1  is not defined   You can define a list containing two lists as follows   arr             Or to define a longer list you could use    gt  gt  gt  arr       for   in range 5    gt  gt  gt  arr                        What you shouldn t do is this   arr          3   As this puts the same list in all three places in the container list    gt  gt  gt  arr 0  append  test    gt  gt  gt  arr    test      test      test

User · Answer

What you re using here are not arrays  but lists  of lists    If you want multidimensional arrays in Python  you can use Numpy arrays  You d need to know the shape in advance   For example    import numpy as np  arr   np empty  3  2   dtype object   arr 0  1     abc

[python] Two dimensional array in python

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