>>> with open('input.txt', 'illegal') as f:
...     for line in f:
...         print line
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: mode string must begin with one of 'r', 'w', 'a' or 'U', not 'illegal'

>>> with open('input.txt', 'rock&roll') as f:
...     for line in f:
...         print line
...
1

2

3

>>> with open('input.txt', 'rock&roll') as f:
...     for line in f:
...         print(line)
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid mode: 'rock&roll'
>>> with open('input.txt', 'illegal') as f:
...     for line in f:
...         print(line)
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid mode: 'illegal'