Script to convert Matlab slices and index to numpy array notation-CodePudding

I am porting some Matlab code to Python. In this code there are many instances of a large matrix being sliced in many different ways, eg M(2:45,13:18), M(:12,:), V(4), V(:27), etc. It is technically possible to convert this to numpy notation manually, by replacing the parentheses with square brackets and substracting 1 to all indices (except after :) but it is incredibly tedious and there is a very high probability that I will make a typo at some point.

I tried automating this but my grep/awk/parsing skills are not good enough. Is there a script out there that will do the job?

CodePudding user response：

Assuming you have your matlab code in a string, you can format it in Python. You could do this with regex match replacement:

import re

def format_indexers(match):
    # Format any "(x:y:z)" into python format
    ret = match[0].replace("(", "[").replace(")", "]") # replace brackets
    ret = re.sub(r"(\d ):", lambda x: str(int(x[1]) - 1)   ":", ret) # replaces numbers by decremented ones
    return ret    

s = "M(2:45,13:18), M(:12,:), V(4), V(:27)"

# Searches expressions between parenthesis and apply format_indexers to found matches
re.sub(r"\(.*\)", format_indexers, s)

outputs:

'M[1:45,12:18], M[:12,:], V[3], V[:27]'

CodePudding user response：

Here is another take based on PlainRavioli's original answer:

INPUT = 'M(2:45,13:18) M(:12,:) V(4) V(:27)'

import re

def my_replace(m):
    m = m.group()
    a, m = m[0], m[2:-1]
    m = m.split(',')
    for k in range(len(m)):
        if ':' in m[k]:
            m[k] = m[k].split(':')
            if m[k][0]:
                m[k][0] = str(int(m[k][0])-1)
            m[k] = ':'.join(m[k])
        else:
            m[k] = str(int(m[k])-1)
    m = ','.join(m)
    m = a   '['   m   ']'
    return m

OUT = re.sub('\\w\\(\d*:?\d*(,\d*:?\d*)?\\)', my_replace, INPUT)
    
print(OUT)
# yields:  M[1:45,12:18] M[:12,:] V[3] V[:27]