Hi, I’m trying to work through python exercises. I’ve written an arithmetic formatter, which seems to work fine on VS Code and now I’m trying to run it on replit, but all I get in my replit console is the following error:

 python3 main.py
Traceback (most recent call last):
  File "/home/runner/boilerplate-arithmetic-formatter-1/main.py", line 2, in <module>
    from pytest import main
ModuleNotFoundError: No module named 'pytest'
exit status 1
So it seems that it can’t find a moudle called “pytest”. These are the contents of my main.py:
# This entrypoint file to be used in development. Start by reading README.md
from pytest import main
from arithmetic_arranger import arithmetic_arranger
import re #I've added this line because my solution uses regex
print(arithmetic_arranger(["32 + 698", "3801 - 2", "45 + 43", "123 + 49"]))
# Run unit tests automatically
main(['-vv'])
I know that some other people had similar problems and had to modify their replit.nix file but so far nothing worked for me.  These are the contents of my replit.nix file:
{ pkgs }: {
  deps = [
    pkgs.python310Full
    pkgs.replitPackages.prybar-python310
    pkgs.replitPackages.stderred
  env = {
    PYTHON_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
      # Needed for pandas / numpy
      pkgs.stdenv.cc.cc.lib
      pkgs.zlib
      # Needed for pygame
      pkgs.glib
      # Needed for matplotlib
      pkgs.xorg.libX11
    PYTHONHOME = "${pkgs.python310Full}";
    PYTHONBIN = "${pkgs.python310Full}/bin/python3.10";
    LANG = "en_US.UTF-8";
    STDERREDBIN = "${pkgs.replitPackages.stderred}/bin/stderred";
    PRYBAR_PYTHON_BIN = "${pkgs.replitPackages.prybar-python310}/bin/prybar-python310";
And lastly here is my arithmetic_formatter, it uses regex so I’ve imported “re” module in my main.py, but I don’t think that’s the problem because even if I remove it and replace the arithmetic_formatter contents with a “Hello world!” program it throws the same error.
def arithmetic_arranger(problems, display=False):
    operators=[]
    operands=[]
    results=[]
    maxLength=[]
    arranged_problems=''
    for item in problems:
        # Checking if input formatting is correct
        if len(problems)>5:
            print('Error: Too many problems.')
            return 'Error: Too many problems.'
        if bool(re.search(' *[\+-] *',item.strip()))==False:
            print('Error: Operator must be \'+\' or \'-\'.')
            return 'Error: Operator must be \'+\' or \'-\'.'
        if bool(re.search('^[0-9]+ *[\+-]',item.strip()))==False or bool(re.search('[\+-] *[0-9]+$',item.strip()))==False:
            print('Error: Numbers must only contain digits.')
            return 'Error: Numbers must only contain digits.'
        if bool(re.search('^[0-9]{1,4} *[\+-]',item.strip()))==False or bool(re.search('[\+-] *[0-9]{1,4}$',item.strip()))==False:
            print('Error: Numbers cannot be more than four digits.')
            return 'Error: Numbers cannot be more than four digits.'
        if bool(re.search('^[0-9]{1,4} *[+-] *[0-9]{1,4}$',item.strip()))==False:
            print('Error: Wrong input.')
            return 'Error: Wrong input'
        #Set up operands, operators, results and their max length
        operands.append(re.split('[\+-]',item))
        if bool(re.search('\+',item)):
            operators.append('add')
        else:
            operators.append('substract')
    for i in range(len(problems)):
        operands[i][0]=int(operands[i][0].strip())
        operands[i][1]=int(operands[i][1].strip())
    for i in range(len(problems)):
        if operators[i]=='add':
            results.append((operands[i][0])+(operands[i][1]))
        else:
            results.append((operands[i][0])-(operands[i][1]))
    for i in range(len(problems)):
        maxLength.append(len(str(max(abs(operands[i][0]),abs(operands[i][1]),abs(results[i])))))
    #Constructing returned string
    for i in range(len(problems)):
        arranged_problems=arranged_problems+' '*2+' '*(maxLength[i]-len(str(abs(operands[i][0]))))+str(operands[i][0])+' '*4
    arranged_problems=arranged_problems+'\n'
    for i in range(len(problems)):
        if operators[i]=='add':
            arranged_problems=arranged_problems+'+'
        else:
            arranged_problems=arranged_problems+'-'
        arranged_problems=arranged_problems+' '+' '*(maxLength[i]-len(str(abs(operands[i][1]))))+str(operands[i][1])+' '*4
    arranged_problems=arranged_problems+'\n'
    for i in range(len(problems)):
        arranged_problems=arranged_problems+'--'+'-'*maxLength[i]+' '*4
    arranged_problems=arranged_problems+'\n'
    for i in range(len(problems)):
        if results[i]>=0:
            arranged_problems=arranged_problems+' '*2+' '*(maxLength[i]-len(str(abs(results[i]))))+str(results[i])+' '*4
        else:
           arranged_problems=arranged_problems+' '+' '*(maxLength[i]-len(str(abs(results[i]))))+str(results[i])+' '*4 
    #print(operators)
    #print(operands)
    #print(results)
    #print(maxLength)
    if display==True:
        print (arranged_problems)
    return arranged_problems
#arithmetic_arranger(["32 + 8", "1 - 3801", "9999 + 9999", "523 - 49"], True)
What do you suggest I should do to make my function run on replit?
              
You might run into this with other packages, same fix could work:
pip install pandas

pip install matplotlib