l = 0
s = 1000000
while True:
num = input("Enter a number: ")
if num == "done": break
try: n = int(num)
except: print('Invalid input')
if n > l: l = n
if n < s: s = n
continue
print("Maximum is", l)
print("Minimum is", s)
while True:
num = input("Enter a number: ")
if num == "done":
break
try:
n = int(num)
except ValueError:
print('Invalid input')
continue
if n > l:
l = n
if n < s:
s = n
Note: it is recommended that conditions go on one line, and solution indented underneath.
Also, use specific except condition, or others will be ignored.