Solutions to https://technology.jana.com/2016/04/26/challenge-your-python-knowledge/

challenge.py

## First  ##########################################
mystery = iter('')
# challenge code
def print_stuff(stuff):
  if stuff:
    print "Printing some stuff"
  for x in stuff:
    print x
  else:
    print "Nothing to print"
print_stuff(mystery)


## Second ##########################################
mystery1 = 1e16
mystery2 = 2e16
# challenge code
def sum_numbers(low, high):
  total = 0
  while low <= high:
    total += low
    low += 1
  return total
# Make sure we are using valid numeric values
assert float('-inf') < mystery1 < float('inf')
assert float('-inf') < mystery2 < float('inf')
print sum_numbers(mystery1, mystery2)
# result:
# Program never terminates


## Third  ##########################################
mystery1 = dict()
mystery2 = {0:mystery1}
mystery1[0]=mystery2
# These are exactly dicts, not subclasses of dict
assert type(mystery1) is dict
assert type(mystery2) is dict

print mystery1 == mystery2

# result:
# RuntimeError: maximum recursion depth exceeded in cmp
# challenge code

## Forth  ##########################################
import random
class Forth(object):
    def __repr__(self): return str(random.random())
mystery1=mystery2={0: Forth()}
# challenge code
assert type(mystery1) is dict
assert type(mystery2) is dict

assert str(mystery1) != str(mystery2)
assert mystery1 == mystery2

print "All checks passed"

# output:
# All checks passed