Random Count Up

import random
from timeit import default_timer as timer
start = timer()
y = [0]
x = 1
f = 1000000
g = 500
z = y[:-1]
d = {}
tot = 0
rolls = 0
rollsmax = 0
rollsmin = 0
highroll = 0
lowroll = None
highkey = 0
lowkey = 0
hightime = 0
lowtime = None
hightimekey = 0
lowtimekey = 0
trange = 0
while y[-1] < g:
    x = random.randint(1, f)
    a = len(str(x))
    b = 4 - a
    z = y[-1]
    rolls += 1
    if x in d:
        d[x] += 1
    else:
        d[x] = 1
    if x == z + 1:
        y.append(x)
        end = timer()
        print(x, ':', rolls)
        if rolls > highroll:
            highroll = rolls
            highkey = y[-1]
            print('The Highest Current Roll was: ', highroll,', for key number: ', highkey)
        if lowroll is None:
            lowroll = rolls
            lowkey = y[-1]
            print('The Lowest Current Roll was: ', lowroll,', for key number: ', lowkey)
        if rolls < lowroll:
            lowroll = rolls
            lowkey = y[-1]
            print('The Lowest Current Roll was: ', lowroll,', for key number: ', lowkey)
        kend = end - start
        if kend > hightime:
            hightime = kend
            hightimekey = y[-1]
        if lowtime is None:
            lowtime = kend
            lowtimekey = y[-1]
        if kend < lowtime:
            lowtime = kend
            lowtimekey = y[-1]
        rolls = 0
    tot += 1
averagerolls = tot / g
ending = timer()
averagetime = (ending - start) / g
rrange = highroll - lowroll
trange = hightime - lowtime
print('Total Rolls is:', tot, ', Total Time is', (ending - start))
print('The Average number of rolls was:', averagerolls)
print('The average time was', (averagetime))
print('The Highest Roll was: ', highroll,', for key number: ', highkey)
print('The Lowest Roll was: ', lowroll,', for key number: ', lowkey)
print('Roll Range was', rrange)
print('The Longest Roll Time was: ', hightime,', for key number: ', hightimekey)
print('The Shortest Roll Time was: ', lowtime,', for key number: ', lowtimekey)
print('The Time Range was:', trange)