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My python loop is either freezing up or running once

The purpose of this program is to have a user input numbers until they enter done, at which point the program outputs the maximum & minimum numbers. If the user enters something that is not a number, the program says "invalid input" and skips to the next time the loop runs. I have a try/except as well. This program is written in Python 3. when I run without the continue at the bottom, my screen freezes & I have to restart. With it, I get a pop-up saying SyntaxError: bad input on line 25.
largest = 0
largest = float(largest)
smallest = 0
smallest = float(smallest)
num = input('Enter a number: ')
num = float(num)
while True:
if num == "done":
break
try:
float(num)
except:
print('Invalid Input')
continue
if num > largest:
largest = num
if smallest == 0:
smallest= num
if smallest > num:
smallest = num
print(num)
continue
print("Maximum is", largest)
print("Minimum is", smallest)

Your input is outside of your loop so it only asks once and since it doesn't ever change its value to "done", it loops forever.
largest = 0
largest = float(largest)
smallest = 0
smallest = float(smallest)
# num = input("Enter a number: ")
while True:
num = input("Enter a number: ")
if num == "done":
break
try:
num = float(num)
float(num)
except:
print("Invalid Input")
continue
if num > largest:
largest = num
if smallest == 0:
smallest = num
if smallest > num:
smallest = num
print(num)
continue
print("Maximum is", largest)
print("Minimum is", smallest)

Finding the largest and the smallest in Python 2.7

I had an assignment, where I let users choose random numbers, and this program would find the smallest and the largest between all these numbers, and if a number is not entered it would consider it an invalid input.
Here's the code I wrote:
largest = None
smallest = None
while True:
inp = raw_input("Enter a number: ")
if inp == 'done': break
if len(inp) < 1: break
try:
num = int(inp)
except:
print "Invalid input"
continue
if smallest is None:
smallest = num
elif inp < smallest:
smallest = num
if largest is None:
largest = num
elif inp > largest:
largest = num
print "Maximum is %r" % (largest)
print "Minimum is %r" % (smallest)
The question is, why is it not working ?
Here's some random numbers I tried and got something weird.
Here I executed the code in the first part and got weird answers, and I executed it again with different numbers and got it right.

You've mixed up < and > and you're comparing inp which is a string to smallest and largest instead of num.

Your indentation is wrong and you made a lot of misprints. Look at this code.
In if-then-else you have to compare num with smallest and largest but not inp.
largest = None
smallest = None
while True:
inp = raw_input("Enter a number: ")
if inp == 'done': break
try:
num = int(inp)
except:
print "Invalid input"
continue
print num
if smallest is None: smallest = num
elif num < smallest: smallest = num
if largest is None: largest = num
elif num > largest: largest = num
print "Maximum is %r" % (largest)
print "Minimum is %r" % (smallest)

Python 2.7 debugging basic code

So I submitted this for a Cousera course on basic python (I'm very very new to writing code). It worked. However, I found a bug in it (which I'm both glad I can see and heartbroken because it exists).
The problem is that if the smallest number in a string of numbers is the first number given it gets absorbed by the largest variable and not into the smallest variable. How would I prevent this from happening?
Thanks in advance!
Code below:
largest = -1
smallest = None
while True:
try:
num = raw_input('number\n')
float(num)
if num > largest:
largest = num
elif smallest is None:
smallest = num
elif smallest > num:
smallest = num
except:
if num =="Done":
print "Maximum is", largest
print "Minimum is", smallest
break
print "Invalid input"

Welcome to the world of programming!
Usually when I do min/max comparisons, I start with negative and positive infinity and not None/null or the first element of the list as that has given me headaches in the past.
This code seems to work fine to me.
largest = float("-inf")
smallest = float("inf")
while True:
try:
num = raw_input('number: ')
num = float(num) # I reassign num for good-measure
if num > largest:
largest = num
if num < smallest:
smallest = num
except:
if num == "Done":
print "Maximum is", largest
print "Minimum is", smallest
break
print "Invalid input"

Purely as an educational exercise, you could use some of python's features (generators) to make this code more generic.
This creates a generator called numbers which returns a sequence of input numbers, that is collected as a list in a and then you can use the builtin min(a), max(a) methods:
def numbers():
while True:
try:
num = input('number\n')
yield float(num)
except ValueError:
if num == "Done":
break
print "Invalid input"
a = list(numbers())
print "Maximum is", max(a)
print "Minimum is", min(a)

You should be able to solve this by setting smallest and largest to the first number input, and doing this before your while loop. That way, for every new number you see, you can update the values of smallest and largest depending on its relative magnitude. Something like this:
largest = -1
smallest = None
try:
num1 = raw_input('number\n')
smallest = num1
largest = num1
while True:
num = raw_input('number\n')
num = float(num)
if num > largest:
largest = num
elif smallest > num:
smallest = num
except:
if num =="Done":
print "Maximum is", largest
print "Minimum is", smallest
break
print "Invalid input"

Python None < 0 = True?

I am trying to do this program that asks the user to input and you select the minimum and maximum of the numbers you put in the problem is it does find the maximum but the minimum shows up as None, any help on this? I just want to understand why None is lower than the numbers I type isn't None suppose to mean that the variable doesn't have any value until num is replaced by the user? thanks.
smallest = None
largest = None
while True:
num = raw_input('Enter the values: ')
if num == 'done' : break
if len(num) < 1 : break
try:
num = int(num)
except:
print 'Invalid input'
continue
if num is None or smallest > num :
smallest = num
if num is None or num > largest :
largest = num
print 'Maximum is',largest
print 'Minimum is',smallest

Python comparisons between different types aren't particularly meaningful. Instead of using None as your sentinel, use a large or small number:
smallest = 1e100
largest = -1e100

How do i print smaller value?

I am very new to python, I write below few lines of code but not able to print smallest number from the input.
largest = 0
smallest = 0
while True:
num = raw_input("Enter a number:")
if num == "done" : break
try:
num = int(num)
except:
print "invalid"
continue
if num is smallest:
smallest = num
if num > largest:
largest = num
print "Minimum", smallest, "Maximum", largest
below is my output, it does print correct largest value (whatever i input) but smallest is always zero.
Enter a number:34
Enter a number:12000
Enter a number:dds
invalid
Enter a number:done
Minimum 0 Maximum 12000=====> see minimum is "0" should be 34?

That's the expected behaviour. In fact, your second statement reads:
smallest = 0
0 is less than 34, so smallest won't be updated.
A possible solution is initializing smallest and largest from the first element read:
largest = None
smallest = None
while True:
num = raw_input("Enter a number:")
if num == "done" : break
try:
num = int(num)
except:
print "invalid"
continue
if smallest is None: # or largest is None, it's the same
smallest = num
largest = num
if num < smallest:
smallest = num
if num > largest:
largest = num
print "Minimum", smallest, "Maximum", largest
Besides, you have what appears to be a typo or a misconception about the operator is. This:
if num is smallest:
smallest = num
Should be:
if num < smallest:
smallest = num