Add those functions to hooks of python-mode and latex-mode
(require 'python)
;; If you use tex-mode
(require 'tex-mode)`
(add-hook 'latex-mode-hook 'flyspell-mode)
;; If you use AUCTeX
(load "auctex.el" nil t t)`
(add-hook 'LaTeX-mode-hook 'flyspell-mode)
(add-hook 'python-mode-hook 'flyspell-prog-mode)