Python greedy graph colourings

import os.path

def checkFile(filename):
    return os.path.isfile(filename)

def checkConsistency(filename):
    inFile = open(filename, 'r')
    character = inFile.read()
    validcharacters = 0
    while not (character == ''):
        if character == '0' or character == '1':
            validcharacters += 1
    size = sqrt(validcharacters)
    if size.is_integer():
        return True, size
    else:
        return False, 0

def adjMatrixToLists(inMat):
    adjlist = []
    for i in range(len(inMat)):
        ilist = []
        for j in range(len(inMat[i])):
            if inMat[i][j] == 1:
                ilist.append(j)
        adjlist.append(ilist)
    return adjlist

def adjListToMatrix(inList):
    matrix = [[0 for x in range(len(inList))] for x in range(len(inList))]
    for i in range(0, len(inList)):
        for j in inList[i]:
            matrix[i][j] = 1
    return matrix

def readGraphIntoMatrix(filename, n):
    inFile = open(filename, 'r')
    matrix = [['3' for x in range(n)] for x in range(n)]

    for i in range(0,n):
        for j in range(0,n):
            matrix[i][j] = int(inFile.read(1))

    return matrix

def printMatrix(matrix):
    for i in matrix:
        for j in i:
            print(j, end="")
        print();


def graphFacts(adjMatrix):
    numVerticies = len(adjMatrix)
    numEdges = 0

    Degrees = [0] * numVerticies

    iIndex = 0
    jIndex = 0

    for i in adjMatrix:
        for j in i:
            if iIndex == jIndex:
                break

            if j == 1:
                numEdges += 1
                Degrees[iIndex] += 1
                Degrees[jIndex] += 1
            jIndex += 1
        jIndex = 0;
        iIndex += 1

    print("Number of verticies:\t", numVerticies);
    print("Number of edges:\t",  numEdges);
    print("\nVertex\tDegree")

    for i in range(0,numVerticies):
        print(i, "\t", Degrees[i])

def greedyColouring1(inList):
    colours = [0] * len(inList)
    for i in range(0, len(inList)):
        adjColours = []
        for j in inList[i]:
            adjColours.append(colours[j])
        colours[i] = max(adjColours) + 1
    print("Coloured using", max(colours), "colours.")
    return colours

def greedyColouring2(inList):
    colours = [0] * len(inList)
    for x in range(0, len(inList)):
        lowestColourDict = {}
        for i in range(0, len(inList)):
            if colours[i] != 0:
                continue
            adjColours = []
            for j in inList[i]:
                adjColours.append(colours[j])
            lowestColourDict[i] = max(adjColours) + 1
        minVert = min(lowestColourDict, key = lowestColourDict.get)
        colours[minVert] = lowestColourDict[minVert]
    print("Coloured using", max(colours), "colours.")
    return colours

def checkColouring(adjList, colours):
    iIndex = 0
    for i in adjList:
        for j in i:
            if colours[j] == colours[iIndex]:
                return False
        iIndex += 1
    return True

matrix = readGraphIntoMatrix("SampleGraphs/CTexampledigraph17.txt", 17)
lists = adjMatrixToLists(matrix)
colours = greedyColouring1(lists)
print("Legit colouring?", checkColouring(lists, colours))
colours = greedyColouring2(lists)
print("Legit colouring?", checkColouring(lists, colours))