Python dodgy file handle modes

write_foo.py

with open('foo', 'w') as foo:
  foo.write("bar\n") # writes bar
  
with open('foo', 'wa') as foo:
  foo.write("baz\n") # writes baz, removes bar
  
with open('foo', 'what will this do?') as foo:
  foo.write("nonsense\n") # removes bar, writes nonsense!
  
with open('foo', 'something else') as foo:
  foo.write("This fails\n") # raises `ValueError: mode string must begin with one of 'r', 'w', 'a' or 'U', not 'something else'`