def main(filemane):
    with open(filemane, 'r') as f:
        hist = {}
        byte_size= 1024
        while True:
            res = f.read(byte_size)
            if res == '':
                break
            for ch in res:
                if ch in hist:
                    hist[ch] += 1
                else:
                    hist[ch] = 1
    print('Hist')
    print(hist)
    new_top = 0
    prev_top = 0
    top_key = 0
    for key in hist:
        new_top = max(hist[key],0)
        if prev_top < new_top:
            top_key = key
            prev_top = new_top

    print('Top key {} with occurance {}'.format(top_key, prev_top))

if __name__ == "__main__":
    filemane = "sample_file.txt"
    main(filemane)