Access python help using pydoc

The syntax is:
pydoc keyword
pydoc3 keyword
pydoc len
pydoc print
Edit your ~/.vimrc:
$ vim ~/.vimrc
Append the following configuration for pydoc3 (python v3.x docs). Create a mapping for H key that works in normal mode:

nnoremap <buffer> H :<C-u>execute "!pydoc3 " . expand("<cword>")<CR>

Save and close the file. Open vim text editor:
$ vim file.py
Write some code:

#!/usr/bin/python3
x=5
y=10
z=x+y
print(z)
print("Hello world")

Position cursor under the print Python keyword and press Shift followed by H. You will see output as follows:

How to view python help when using vim

jedi-vim is a VIM binding to the autocompletion library Jed. It can do many things including display help for keyword when you press Shift followed by K i.e. press capital K.

How to install jedi-vim on Linux or Unix-like system

Use pathogen, vim-plug or Vundle to install jedi-vim. I am using Vim-Plug. Add the following line in ~/vimrc:
Plug 'davidhalter/jedi-vim'
Save and close the file. Start vim and type:
PlugInstall
On Arch Linux, you can also install jedi-vim from official repositories as vim-jedi using pacman command:
$ sudo pacman -S vim-jedi
It is also available on Debian (?8) and Ubuntu (?14.04) as vim-python-jedi using apt command/apt-get command:
$ sudo apt install vim-python-jedi
On Fedora Linux, it is available as vim-jedi using dnf command:
$ sudo dnf install vim-jedi
Jedi is by default automatically initialized. So no further configuration needed on your part. To see Documentation/Pydoc press K. It shows a popup with assignments: