Why python docstring is interpreted differently from comment

Question

Let\'s say, I\'ve got a function like this:

def myFunc():
    # useful function to calculate stuff

This will produce an indentation error, unle

Answer 1

A comment is outright ignored by the interpreter, so omitting a block after an indent is a syntax error. However, a docstring is a real Python object--at its most basic, a literal str. A lone expression is a valid block of code:

'This is a string. It is a valid (though pretty useless) line of Python code.'

In the case of docstrings in particular, there's also some additional functionality going on, such as being used to set the __doc__ attribute.

>>> def myFunc():
...     '''MyDocString'''
...
>>> print(myFunc.__doc__)
MyDocString

Note that this also works for classes:

>>> class MyClass(object):
...     '''MyClassDocString'''
...
>>> print(MyClass.__doc__)
MyClassDocString