From Matlab to Python

Important commands

The for-loop

Matlab:

for i = 1:10
    disp(i)
end

Matlab requires the end key-word at the end of the block belonging to the for-loop.

Python:

for i in range(1,11):
    print(i)

1
2
3
4
5
6
7
8
9
10

Python requires a colon (“:”) at the of the for-line. (This is important and often forgotten when you have programmed in Matlab before.) Python requires the commands to be executed within the for-loop to be indented.

The if-then statement

Matlab:

if a==0
    disp('a is zero')
elseif a<0
    disp('a is negative')
elseif a==42
    disp('a is 42')
else
    disp('a is positive')
end

Matlab requires the end key-word at the very end of the block belonging to the for-loop.

Python:

a = -5

if a==0:
    print('a is zero')
elif a<0:
    print('a is negative')
elif a==42:
    print('a is 42')
else:
    print('a is positive')

a is negative

Python requires a colon (“:”) after every condition (i.e. at the of the lines starting with if, elif, else. Python requires the commands to be executed within each part of the if-then-else statement to be indented.

Indexing

Matlab’s indexing of matrices and vectors starts a 1 (similar to Fortran), whereas Python’s indexing starts at 0 (similar to C).

Matrices

In Matlab, every object is a matrix. In Python, there is a specialised extension library called numpy (see Sec. [cha:numer-pyth-numpy]) which provides the array object which in turns provides the corresponding functionality. Similar to Matlab, the numpy object is actually based on binary libraries and execution there very fast.

There is a dedicated introduction to numpy for Matlab users available at https://docs.scipy.org/doc/numpy-dev/user/numpy-for-matlab-users.html.