Matrix Transpose in Python
PythonListMultidimensional ArrayPython Problem Overview
I am trying to create a matrix transpose function for python but I can't seem to make it work. Say I have
theArray = [['a','b','c'],['d','e','f'],['g','h','i']]
and I want my function to come up with
newArray = [['a','d','g'],['b','e','h'],['c', 'f', 'i']]
So in other words, if I were to print this 2D array as columns and rows I would like the rows to turn into columns and columns into rows.
I made this so far but it doesn't work
def matrixTranspose(anArray):
transposed = [None]*len(anArray[0])
for t in range(len(anArray)):
for tt in range(len(anArray[t])):
transposed[t] = [None]*len(anArray)
transposed[t][tt] = anArray[tt][t]
print transposed
Python Solutions
Solution 1 - Python
Python 2:
>>> theArray = [['a','b','c'],['d','e','f'],['g','h','i']]
>>> zip(*theArray)
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', 'f', 'i')]
Python 3:
>>> [*zip(*theArray)]
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', 'f', 'i')]
Solution 2 - Python
>>> theArray = [['a','b','c'],['d','e','f'],['g','h','i']]
>>> [list(i) for i in zip(*theArray)]
[['a', 'd', 'g'], ['b', 'e', 'h'], ['c', 'f', 'i']]
the list generator creates a new 2d array with list items instead of tuples.
Solution 3 - Python
If your rows are not equal you can also use map:
>>> uneven = [['a','b','c'],['d','e'],['g','h','i']]
>>> map(None,*uneven)
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', None, 'i')]
Edit: In Python 3 the functionality of map changed, itertools.zip_longest can be used instead:
Source: http://docs.python.org/3/whatsnew/3.0.html#views-and-iterators-instead-of-lists">What’s New In Python 3.0
>>> import itertools
>>> uneven = [['a','b','c'],['d','e'],['g','h','i']]
>>> list(itertools.zip_longest(*uneven))
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', None, 'i')]
Solution 4 - Python
Much easier with numpy:
>>> arr = np.array([[1,2,3],[4,5,6],[7,8,9]])
>>> arr
array([[1, 2, 3],
[4, 5, 6],
[7, 8, 9]])
>>> arr.T
array([[1, 4, 7],
[2, 5, 8],
[3, 6, 9]])
>>> theArray = np.array([['a','b','c'],['d','e','f'],['g','h','i']])
>>> theArray
array([['a', 'b', 'c'],
['d', 'e', 'f'],
['g', 'h', 'i']],
dtype='|S1')
>>> theArray.T
array([['a', 'd', 'g'],
['b', 'e', 'h'],
['c', 'f', 'i']],
dtype='|S1')
Solution 5 - Python
The problem with your original code was that you initialized transpose[t] at every element, rather than just once per row:
def matrixTranspose(anArray):
transposed = [None]*len(anArray[0])
for t in range(len(anArray)):
transposed[t] = [None]*len(anArray)
for tt in range(len(anArray[t])):
transposed[t][tt] = anArray[tt][t]
print transposed
This works, though there are more Pythonic ways to accomplish the same things, including @J.F.'s zip application.
Solution 6 - Python
To complete J.F. Sebastian's answer, if you have a list of lists with different lengths, check out this great post from ActiveState. In short: > The built-in function zip does a similar job, but truncates the result > to the length of the shortest list, so some elements from the original > data may be lost afterwards.
To handle list of lists with different lengths, use:
def transposed(lists):
if not lists: return []
return map(lambda *row: list(row), *lists)
def transposed2(lists, defval=0):
if not lists: return []
return map(lambda *row: [elem or defval for elem in row], *lists)
Solution 7 - Python
The "best" answer has already been submitted, but I thought I would add that you can use nested list comprehensions, as seen in the Python Tutorial.
Here is how you could get a transposed array:
def matrixTranspose( matrix ):
if not matrix: return []
return [ [ row[ i ] for row in matrix ] for i in range( len( matrix[ 0 ] ) ) ]
Solution 8 - Python
This one will preserve rectangular shape, so that subsequent transposes will get the right result:
import itertools
def transpose(list_of_lists):
return list(itertools.izip_longest(*list_of_lists,fillvalue=' '))
Solution 9 - Python
you can try this with list comprehension like the following
matrix = [['a','b','c'],['d','e','f'],['g','h','i']] n = len(matrix) transpose = [[row[i] for row in matrix] for i in range(n)] print (transpose)
Solution 10 - Python
If you want to transpose a matrix like A = np.array([[1,2],[3,4]]), then you can simply use A.T, but for a vector like a = [1,2], a.T does not return a transpose! and you need to use a.reshape(-1, 1), as below
import numpy as np
a = np.array([1,2])
print('a.T not transposing Python!\n','a = ',a,'\n','a.T = ', a.T)
print('Transpose of vector a is: \n',a.reshape(-1, 1))
A = np.array([[1,2],[3,4]])
print('Transpose of matrix A is: \n',A.T)
Solution 11 - Python
You may do it simply using python comprehension.
arr = [ ['a', 'b', 'c'],
['d', 'e', 'f'],
['g', 'h', 'i']
]
transpose = [[arr[y][x] for y in range(len(arr))] for x in range(len(arr[0]))]
Solution 12 - Python
def matrixTranspose(anArray):
transposed = [None]*len(anArray[0])
for i in range(len(transposed)):
transposed[i] = [None]*len(transposed)
for t in range(len(anArray)):
for tt in range(len(anArray[t])):
transposed[t][tt] = anArray[tt][t]
return transposed
theArray = [['a','b','c'],['d','e','f'],['g','h','i']]
print matrixTranspose(theArray)
Solution 13 - Python
import numpy as np #Import Numpy
m=int(input("Enter row")) #Input Number of row
n=int(input("Enter column")) #Input number of column
a=[] #Blank Matrix
for i in range(m): #Row Input
b=[] #Blank List
for j in range(n):#column Input
j=int(input("Enter Number in Pocket ["+str(i)+"]["+str(j)+"]")) #sow Row Column Number
b.append(j) #addVlaue to list
a.append(b)#Add List To Matrix
a=np.array(a)#convert 1matrix as Numpy
b=a.transpose()#transpose Using Numpy
print(a) #Print Matrix
print(b)#print Transpose Matrix
Solution 14 - Python
#generate matrix
matrix=[]
m=input('enter number of rows, m = ')
n=input('enter number of columns, n = ')
for i in range(m):
matrix.append([])
for j in range(n):
elem=input('enter element: ')
matrix[i].append(elem)
#print matrix
for i in range(m):
for j in range(n):
print matrix[i][j],
print '\n'
#generate transpose
transpose=[]
for j in range(n):
transpose.append([])
for i in range (m):
ent=matrix[i][j]
transpose[j].append(ent)
#print transpose
for i in range (n):
for j in range (m):
print transpose[i][j],
print '\n'
Solution 15 - Python
a=[]
def showmatrix (a,m,n):
for i in range (m):
for j in range (n):
k=int(input("enter the number")
a.append(k)
print (a[i][j]),
print('\t')
def showtranspose(a,m,n):
for j in range(n):
for i in range(m):
print(a[i][j]),
print('\t')
a=((89,45,50),(130,120,40),(69,79,57),(78,4,8))
print("given matrix of order 4x3 is :")
showmatrix(a,4,3)
print("Transpose matrix is:")
showtranspose(a,4,3)
Solution 16 - Python
def transpose(matrix):
x=0
trans=[]
b=len(matrix[0])
while b!=0:
trans.append([])
b-=1
for list in matrix:
for element in list:
trans[x].append(element)
x+=1
x=0
return trans
Solution 17 - Python
def transpose(matrix):
listOfLists = []
for row in range(len(matrix[0])):
colList = []
for col in range(len(matrix)):
colList.append(matrix[col][row])
listOfLists.append(colList)
return listOfLists
Solution 18 - Python
`
def transpose(m):
return(list(map(list,list(zip(*m)))))
`This function will return the transpose
Solution 19 - Python
Python Program to transpose matrix:
row,col = map(int,input().split())
matrix = list()
for i in range(row):
r = list(map(int,input().split()))
matrix.append(r)
trans = [[0 for y in range(row)]for x in range(col)]
for i in range(len(matrix[0])):
for j in range(len(matrix)):
trans[i][j] = matrix[j][i]
for i in range(len(trans)):
for j in range(len(trans[0])):
print(trans[i][j],end=' ')
print(' ')