Why does help(42) work but neither help("") nor help("x")? [duplicate]

Question

Possible Duplicate:
Inconsistency in python help(‘string’) versus help(list)?

In the interactive shell of Python, if I type help(42) I get all the information about int objects. If I type help("") I get nothing and if I type help("x") I get "no Python documentation found for 'x'".

I know I can type help(str), but I'd like to understand why are the other two working differently from help(42)?

Answer 1

See the documentation on the help function:

If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.

In other words, when help is given a class or type, it returns help on that class or type.

class C: pass
help(C)

When help is given any instance other than a string, like help(1), it provides documentation on the type of that variable (int, float, or a defined class).

help(1)
help(C())

When it is given a string, it provides documentation on the type or class that that string refers to. If you want help with the str class itself, you can do:

help(str)

or

help("str")