My first Python programme (of any merit)

whalers.py

import csv, re


def readHeightsFile(path):
    heights = []

    with open(path, "r", encoding = "utf-8", errors = "ignore") as csvFile:
        f1 = csv.DictReader(csvFile)
        for row in f1:
            heights.append(row["Height"])

    print('Read ', len(heights), ' records')

    return heights


def convertFrac(f):
    """Tries to convert a supposed fraction into a decimal number

    Keyword Arguments:
        f -- a string contianing the fraction
    """
    patternFrac = re.compile("^ ?([0-9]+)/([0-9]+)$")
    patternDec = re.compile("^(\.[0-9]+)$")

    matchFrac = patternFrac.match(f)
    matchDec = patternDec.match(f)

    if matchFrac:
        numerator = float(matchFrac.group(1))
        denominator = float(matchFrac.group(2))

        if numerator < denominator:
            return numerator / denominator
        else:
            return -1
    elif matchDec:
        d = float(f)
        if 0 < d < 1:
            return d
        else:
            return -1
    else:
        return -1

def convInchesToMillimetres(x):
    ## clean up some obvious problems before trying to match
    x = re.sub("[\"\-]", "", x)
    x = re.sub("^ *$", x, "")
    x = re.sub("^(5|6)\'([1-9]|10|11)*([13]/[248]).*$", "\1\'\2 \3", x)
    x = re.sub("^5\'5(7|9)(.*$)", "5\'\1\2", x)

    if re.match("^ *$", x):
        return -1

    pattern = re.compile("^ *([1-7]) *(ft[.\']?|\'{1,2}|[,;.])? *([0-9]{1,2})? *([\'t]|in\.*)?([ ]+(1/2|([12])/3|(1|3)/4|([15])/6|([1-7])/8|1/12)|(\.?[0-9]{1,3}))?[ +\?`l (2)]*$")

    m = pattern.match(x)



    def toMillimetres(feet, inches, frac = 0):
        """Converts feet, inches, fractions of an inch to millimeters

        Keyword Arguments:
            feet -- the number of feet in the measurement
            inches -- the number of inches in the measurement
            frac -- fractions of an inch, either in fraction form or decimal form
        """
        return (feet * 12 + inches + frac) * 25.4

    if m:
        feet = 0
        inches = 0

        if not(m.group(1) is None):
            feet = float(m.group(1))

        if not(m.group(3) is None):
            inches = float(m.group(3))

        if feet == 0 and inches == 0:
            print("Couldn't resolve this measurement: ", x)
            return 0

        frac = 0

        if m.group(5):
            frac = convertFrac(m.group(5))

            if 0 < frac < 1:
                return toMillimetres(feet, inches, frac)
            else:
                print("Couldn't resolve this fraction: ", m.group(5))
                print("Using 0 instead")
                return toMillimetres(feet, inches)

        return toMillimetres(feet, inches, frac)
    else:
        print("Couldn't resolve this measurement:", h)
        return 0



myFile = "/users/jcur002/Dropbox/Work/2017/779/crewlist.csv"
heights = readHeightsFile(myFile)
hmm = []

#for h in heights:
#    hmm.append(convInchesToMillimetres(h))
convInchesToMillimetres("6 ' 11/2")