python: raising exception from inside of generator function.

gistfile1.py

# -*- coding: utf-8 -*-
# simple generator function
def generator1(limit):
  for count in range(limit):
    yield count

# simple generator function with return
def generator2(limit, stop):
  for count in range(limit):
    if count > stop:
      return
    yield count

# simple generator function raising exception
def generator3(limit, stop):
  for count in range(limit):
    if count > stop:
      raise
    yield count

# simple generator function raising custom exception
def generator4(limit, stop):
  class TempException(Exception):
    pass
  for count in range(limit):
    if count > stop:
      raise  TempException
    yield count


print 'generator1(5)'
gen1 = generator1(5)
while True:
  try:
    print gen1.next()
  except Exception, ex:
    print type(ex)
    break
print 'StopIteration at the end of generator'
print ''

print 'generator2(5, 3)'
gen2 = generator2(5, 3)
while True:
  try:
    print gen2.next()
  except Exception, ex:
    print type(ex)
    break
print 'StopIteration raised when generator returns'
print ''


print 'generator3(5, 3)'
gen3 = generator3(5, 3)
while True:
  try:
    print gen3.next()
  except Exception, ex:
    print type(ex)
    break
print 'StopIteration raised when generator raises Exception'
print ''


print 'generator4(5, 3)'
gen4 = generator4(5, 3)
while True:
  try:
    print gen4.next()
  except Exception, ex:
    print type(ex)

  try:
    print gen4.next()
  except Exception, ex:
    print type(ex)
    break

print 'First, TempException raised when generator raises TempException, and next gen4.next() call gets StopIteration'
print ''

output

generator1(5)
0
1
2
3
4
<type 'exceptions.StopIteration'>
StopIteration at the end of generator

generator2(5, 3)
0
1
2
3
<type 'exceptions.StopIteration'>
StopIteration raised when generator returns

generator3(5, 3)
0
1
2
3
<type 'exceptions.StopIteration'>
StopIteration raised when generator raises Exception

generator4(5, 3)
0
1
2
3
<class '__main__.TempException'>
<type 'exceptions.StopIteration'>
First, TempException raised when generator raises TempException, and next gen4.next() call gets StopIteration