Syntastic (vim-plugin) works for c++ and c, but not for Python, html, css

Question

I recently got Syntastic (got it by vim-plug, Plug 'vim-syntastic/syntastic') and it works for c++ and c. Example: What I used:

let g:syntastic_cpp_checkers = ['gcc']

And when I use Python or HTML or CSS.

Example(with Python): What I used:

let g:syntastic_python_checkers = ['bandit', 'python']

And same problem is with other languages.

Edit:

:SyntasticInfo for python
Syntastic version: 3.9.0-9 (Vim 704, Linux)
Info for filetype: python
Global mode: active
Filetype python is active
The current file will be checked automatically
Available checker: python
Currently enabled checker: python