How does it know that a line pasted to the end of a block from another indentation level belongs to that block or should go after the end of the block?
if cond:
line
pasted line # where does it go?
Regardless of whom or what is doing the indentation, people still prefer reading code which is indented, even in a language which relies on braces or parenthesis for flow. The indenting is not for the compiler's sake, it has no problem understanding this: http://www.ioccc.org/2014/maffiodo1/prog.c
Also people get very picky and personal when it comes to indentation in ways that a computer can't always choose. I prefer to almost always indent and format my code myself, rather than letting the editor choose. Python is the only language I actually let my editor auto-format, because of PEP-8.
> Is there any automatical indentation function in some editor for Python?
Pretty much any editor will have a feature for this, or allow you to install a popular plugin for it in less than a minute.