How to make matrices in Python

Question

I ve googled it and searched StackOverflow and YouTube   I just can t get matrices in Python to click in my head  Can someone please help me  I m just trying to create a basic 5x5 box that displays   A A A A A B B B B B C C C C C D D D D D E E E E E   I got  a b c d e a b c d e a b c d e a b c d e a b c d e   To display but I couldn t even get them to break lines that  instead all they would appear as      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E      And if I try to add  n to them or print    etc it just doesn t work    n will display as  A n  and print will display before the matrix   Please someone help me  even if you direct me to somewhere that should be really obvious and make me look like an idiot  I just want to learn this

User · Answer

If you don t want to use numpy  you could use the list of lists concept  To create any 2D array  just use the following syntax     mat     input   for i in range  col   for j in range  row     and then enter the values you want

User · Answer

you can do it short like this   matrix      A  B  C  D  E   5  print matrix       A  B  C  D  E    A  B  C  D  E    A  B  C  D  E    A  B  C  D  E    A  B  C  D  E

User · Answer

Looping helps   for row in matrix      print     join row    or use nested str join   calls   print   n  join      join row  for row in matrix     Demo    gt  gt  gt  matrix      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E      A    B    C    D    E     gt  gt  gt  for row in matrix          print     join row       A B C D E A B C D E A B C D E A B C D E A B C D E  gt  gt  gt  print   n  join      join row  for row in matrix   A B C D E A B C D E A B C D E A B C D E A B C D E   If you wanted to show the rows and columns transposed  transpose the matrix by using the zip   function  if you pass each row as a separate argument to the function  zip   recombines these value by value as tuples of columns instead  The  args syntax lets you apply a whole sequence of rows as separate arguments    gt  gt  gt  for cols in zip  matrix      transposed         print     join cols       A A A A A B B B B B C C C C C D D D D D E E E E E

User · Answer

I got a simple fix to this by casting the lists into strings and performing string operations to get the proper print out of the matrix   Creating the function  By creating a function  it saves you the trouble of writing the for loop every time you want to print out a matrix   def print matrix matrix       for row in matrix          new row   str row          new row   new row replace                 new row   new row replace                 new row   new row replace                 print new row    Examples  Example of a 5x5 matrix with 0 as every entry    gt  gt  gt  test matrix     0    5 for i in range 5    gt  gt  gt  print matrix test matrix  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    Example of a 2x3 matrix with 0 as every entry    gt  gt  gt  test matrix     0    3 for i in range 2    gt  gt  gt  print matrix test matrix  0 0 0 0 0 0     EDIT  If you want to make it print   A A A A A B B B B B C C C C C D D D D D  E E E E E   I suggest you just change the way you enter your data into your lists within lists  In my method  each list within the larger list represents a line in the matrix  not columns

User · Answer

you can also  use append function   b        for x in range 0  5       b append   O     5   def print b b       for row in b          print     join row

User · Answer

The answer to your question depends on what your learning goals are  If you are trying to get matrices to  click  so you can use them later  I would suggest looking at a Numpy array instead of a list of lists  This will let you slice out rows and columns and subsets easily  Just try to get a column from a list of lists and you will be frustrated    Using a list of lists as a matrix     Let s take your list of lists for example   L    list  ABCDE   for i in range 5     It is easy to get sub-elements for any row    gt  gt  gt  L 1  0 3    A    B    C     Or an entire row    gt  gt  gt  L 1       A    B    C    D    E     But try to flip that around to get the same elements in column format  and it won t work      gt  gt  gt  L 0 3  1    A    B    C    D    E     gt  gt  gt  L    1    A    B    C    D    E     You would have to use something like list comprehension to get all the 1th elements       gt  gt  gt   x 1  for x in L    B    B    B    B    B     Enter matrices  If you use an array instead  you will get the slicing and indexing that you expect from MATLAB or R   or most other languages  for that matter     gt  gt  gt  import numpy as np  gt  gt  gt  Y   np array list  ABCDE  5   reshape 5 5   gt  gt  gt  print Y    A   B   C   D   E      A   B   C   D   E      A   B   C   D   E      A   B   C   D   E      A   B   C   D   E     gt  gt  gt  print Y transpose      A   A   A   A   A      B   B   B   B   B      C   C   C   C   C      D   D   D   D   D      E   E   E   E   E      Grab row 1  as with lists     gt  gt  gt  Y 1    array   A    B    C    D    E           dtype   S1     Grab column 1  new      gt  gt  gt  Y   1  array   B    B    B    B    B           dtype   S1     So now to generate your printed matrix   for mycol in Y transpose        print     join mycol    A A A A A B B B B B C C C C C D D D D D E E E E E

[python] How to make matrices in Python?

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