data = [('Cape Town - Durban','RT',95),
        ('Cape Town - Durban','RT',95),
        ('Cape Town - Durban','BT',185),
        ('Cape Town - Durban','BE',285),
        ('Cape Town - Durban','RT',100),
        ('Cape Town - Durban','BT',190),
        ('Cape Town - Durban','BE',290),]
delay={}
# naive implementation
for path,cos,ms in data:
    if not cos in delay:
        delay[cos] = {path: {ms:1}}
    elif not path in delay[cos]:
        delay[cos][path] = {ms:1}
    elif not ms in delay[cos][path]:
        delay[cos][path][ms] = 1
    else:
        delay[cos][path][ms]+= 1

delay={}
# setdefault implementation
for path,cos,ms in data:
    delay.setdefault(cos, {}).setdefault(path, {}).setdefault(ms,0)
    delay[cos][path][ms]+= 1

for cos in delay.keys():
    for path,values in delay[cos].items():
        histogram=[]
        # looping around the test data range for demonstration purposes
        for i in range(90,300):
            # using setdefault has the side-effect of padding the delay dict for non-existent samples
            histogram.append(str(delay[cos][path].setdefault(i, 0)))
        print '%s: %s: %s' % (cos,path,' '.join(histogram))