Check if a file exists.

[Pedroski55]

I need to look for a file in this path:

pathToAnswersHW = '/home/pedro/' + termName[0] + '/' + theClass[0] + '/correctAnswersHW/'

but sometimes this file

theAnswersHW = open(pathToAnswersHW + 'correctAnswersHW' + theClass[0] + answersWeeknumber[0] + '.txt', 'r')

will not exist.

I think there must be some 'os.if_not_exists(file)' I can just return from the function.

What is the best way to check if the file exists?

def openAnswersHW():
    pathToAnswersHW = '/home/pedro/' + termName[0] + '/' + theClass[0] + '/correctAnswersHW/'
    # HW get the correct HW answers with answerDataHW = theAnswersHW.readlines()
    theAnswersHW = open(pathToAnswersHW + 'correctAnswersHW' + theClass[0] + answersWeeknumber[0] + '.txt', 'r')
    # check if the file exists
    
    #put a return in here if the file does not exist

    answerDataHW = theAnswersHW.readlines()
    theAnswersHW.close()
    # HW standardize the apostrophes
    aposSorted = changeApostrophe(answerDataHW)
    echoMessage('Apostrophes sorted ... ')
    for word in aposSorted:            
        answersHW.append(word)        
    echoMessage('answersHW is: ' + str(len(answersHW)) + ' long.')
    echoMessage('Now click "tidy student answers CW" or "tidy student answers HW"')