Python parser for a (simple) LaTeX file - Python

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Python parser for a (simple) LaTeX file

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JeT

**My question**

How do I handle the extraction of the `.tex` file (as described below) to a flat `.csv` with format below ? 

**Posted here originally**

[TeX_TA ](https://topanswers.xyz/tex?q=1521)

**Context**

I created all my MCQ with the `exam` package. However, exams are now 100% online... (sigh)

My LaTeX file has the basic following format

```
\documentclass[12pt]{exam}

\begin{document}

\begin{questions}
 \question What is the answer ? 
 \begin{oneparchoices}
 \choice 70
 \choice 75
 \choice 80
 \CorrectChoice 85
 \choice None of the above
 \end{oneparchoices}

 \question What is the answer to the second question ? 
 \begin{oneparchoices}
 \choice 70
 \choice 75
 \CorrectChoice 80
 \choice 85
 \choice None of the above
 \end{oneparchoices}

\end{questions}
\end{document}
```

I need now to provide a csv where the questions of the MCQ above would be displayed like (`Incorrect`,`Correct`, just to be clear 😃 )

`question,answer1,Cor/Inc,answer2,Cor/Inc,answer3,Cor/Inc ,answer4,Cor/Inc,answer5,Cor/Inc`

And it would render like

`What is the answer ?,70,Inc,75,Inc,80,Inc,85,Cor,None of the above,Inc`

Each line would obviously be a new question.

What could correspond so far

I found something interesting in python, but I am more open to a solution than a type of programming.

I see the principle for environment between \begin and \end thanks to https://stackoverflow.com/questions/11054008/extract-figures-from-latex-file

```
infile = open('MCQ.tex', 'r')
outfile = open('FlattenMCQ.csv', 'w')
extract_block = False
for line in infile:
    if 'begin{questions}' in line:
        extract_block = True
    if extract_block:
        outfile.write(line)
    if 'end{questions}' in line:
        extract_block = False
        outfile.write("------------------------------------------\n\n")

infile.close()
outfile.close()
```

Where I am stuck The recurisivity to test first `\begin{questions}` then `\question` then `\begin{oneparchoices}` then `\choice` or `\CorrectChoice`

Top Answer

wizzwizz4

This code's *very* messy, and only parses TeX in the very specific format you've provided, and won't always give you errors if the input document is “malformed”, but it should work:

```python
import csv
from functools import partial
from itertools import takewhile

def questions(lines):
    lines = iter(lines)
    for line in lines:
        if r'\begin{questions}' in line:
            break
    while True:
        for line in lines:
            if r'\end{questions}' in line:
                return
            q = line.split(r'\question', maxsplit=1)
            if len(q) == 2:
                question = q[1].strip()
                break
        if r'\begin{oneparchoices}' not in next(lines):
            raise ValueError(r"Expected \begin{oneparchoices}")
        yield question, tuple(
            (answer.strip(), r'Correct' in choice)
            for choice, answer in map(
                partial(str.split, maxsplit=1),
                takewhile(
                    lambda line: r'\end{oneparchoices}' not in line,
                    lines
                )
            )
        )

def q_flatten(questions):
    for question, answers in questions:
        yield (question,) + tuple(a_flatten(answers))

def a_flatten(answers):
    for answer, correct in answers:
        yield answer
        if correct:
            yield 'Cor'
        else:
            yield 'Inc'

with open('MCQ.tex') as in_, \
     open('FlattenMCQ.csv', 'w', newline='') as out:
    writer = csv.writer(out)
    # If you want a header, add it here.
    ##writer.writerow(("column1", "column2", "etc."))
    writer.writerows(q_flatten(questions(in_)))
```

Answer #2

wizzwizz4

If you have `pip`, and can install the `TexSoup` package (pick one):

```sh
> py -3 -m pip install TexSoup
$ python3 -m pip install TexSoup
$ python -m pip install TexSoup
```

then this would _probably_ be more resilient to TeX formatting changes, but needs to load the entire file into memory so wouldn't work for as large quizzes.

```python
import csv

from TexSoup import TexSoup

def questions(tex):
    soup = TexSoup(tex)
    i = iter(soup[-1][0])  # \begin{questions}
    while True:
        try:
            next(i)  # skip over \question
        except StopIteration:
            return
        question = next(i).strip()
        answers = tuple(
            (answer.strip(), choice.name == 'CorrectChoice')
            for choice, answer in zip(*(2*(iter(next(i)),)))
        )
        yield question, answers

# The below is the same as my other answer:
def q_flatten(questions):
    for question, answers in questions:
        yield (question,) + tuple(a_flatten(answers))

def a_flatten(answers):
    for answer, correct in answers:
        yield answer
        if correct:
            yield 'Cor'
        else:
            yield 'Inc'

with open('MCQ.tex') as in_, \
     open('FlattenMCQ.csv', 'w', newline='') as out:
    writer = csv.writer(out)
    # If you want a header, add it here.
    ##writer.writerow(("column1", "column2", "etc."))
    writer.writerows(q_flatten(questions(in_)))
```

2 Answers