First time poster. My small team just put together a simple prototype for an 'Intro to game development' type game and we'd love to get feedback on it on things to improve or refactor. Thanks.

Git: https://github.com/PygameProjects/battleship

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Importing pygame modules
import random, sys, pygame
from pygame.locals import *


# Set variables, like screen width and height 
# globals
FPS = 30
REVEALSPEED = 8
WINDOWWIDTH = 800
WINDOWHEIGHT = 600
TILESIZE = 40
BUTTONHEIGHT = 20
BUTTONWIDTH = 40
TEXT_HEIGHT = 25
TEXT_LEFT_POSN = 10
BOARDWIDTH = 12
BOARDHEIGHT = 12
DISPLAYWIDTH = 200
XMARGIN = int((WINDOWWIDTH - (BOARDWIDTH * TILESIZE) - (DISPLAYWIDTH + 20)) / 2)
YMARGIN = int((WINDOWHEIGHT - (BOARDHEIGHT * TILESIZE)) / 2)

BLACK   = (  0,   0,   0)
WHITE   = (255, 255, 255)
GREEN   = (  0, 204,   0)
GRAY    = ( 60,  60,  60)
BLUE    = (  0,  50, 255)
YELLOW  = (255, 255,   0)
DARKGRAY =( 40,  40,  40)

BGCOLOR = GRAY
BUTTONCOLOR = GREEN
TEXTCOLOR = WHITE
TILECOLOR = GREEN
BORDERCOLOR = BLUE
TEXTSHADOWCOLOR = BLUE
SHIPCOLOR = YELLOW
HIGHLIGHTCOLOR = BLUE


def main():
    global DISPLAYSURF, FPSCLOCK, BASICFONT, HELP_SURF, HELP_RECT, NEW_SURF, \
           NEW_RECT, SHOTS_SURF, SHOTS_RECT, BIGFONT, COUNTER_SURF, \
           COUNTER_RECT
    pygame.init()
    FPSCLOCK = pygame.time.Clock()
    DISPLAYSURF = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT))
    BASICFONT = pygame.font.Font('freesansbold.ttf', 20)
    BIGFONT = pygame.font.Font('freesansbold.ttf', 100)
    
    # create buttons
    HELP_SURF = BASICFONT.render("HELP", True, WHITE)
    HELP_RECT = HELP_SURF.get_rect()
    HELP_RECT.topleft = (WINDOWWIDTH - 180, WINDOWHEIGHT - 350)
    NEW_SURF = BASICFONT.render("NEW GAME", True, WHITE)
    NEW_RECT = NEW_SURF.get_rect()
    NEW_RECT.topleft = (WINDOWWIDTH - 200, WINDOWHEIGHT - 200)

    # 'Shots:' label
    SHOTS_SURF = BASICFONT.render("Shots: ", True, WHITE)
    SHOTS_RECT = SHOTS_SURF.get_rect()
    SHOTS_RECT.topleft = (WINDOWWIDTH - 750, WINDOWHEIGHT - 570)
    
    pygame.display.set_caption('Battleship')

    while True:
        run_game()
        show_text_screen('Game Over')
        
        
def run_game():
    revealed_tiles = generate_default_tiles(False)
    main_board = generate_default_tiles((None, None))
    ship_objs = make_ships() # list of ships to be used, holds list of tuples
                             # of coords
    main_board = add_ships_to_board(main_board, ship_objs)
    mousex, mousey = 0, 0
    counter = [] # counter to track number of shots fired
        
    while True:
        # counter display (it needs to be here in order to refresh it)
        COUNTER_SURF = BASICFONT.render(str(len(counter)), True, WHITE)
        COUNTER_RECT = SHOTS_SURF.get_rect()
        COUNTER_RECT.topleft = (WINDOWWIDTH - 680, WINDOWHEIGHT - 570)
        # end of the counter
        DISPLAYSURF.fill(BGCOLOR)        
        DISPLAYSURF.blit(HELP_SURF, HELP_RECT)
        DISPLAYSURF.blit(NEW_SURF, NEW_RECT)
        DISPLAYSURF.blit(SHOTS_SURF, SHOTS_RECT)
        DISPLAYSURF.blit(COUNTER_SURF, COUNTER_RECT)
        draw_board(main_board, revealed_tiles)
        mouse_clicked = False     

        check_for_quit()
        for event in pygame.event.get():
            if event.type == MOUSEBUTTONUP:
                if HELP_RECT.collidepoint(event.pos):
                    DISPLAYSURF.fill(BGCOLOR)
                    show_help_screen()
                elif NEW_RECT.collidepoint(event.pos):
                    main()
                else:
                    mousex, mousey = event.pos
                    mouse_clicked = True
            elif event.type == MOUSEMOTION:
                mousex, mousey = event.pos
                    
        tilex, tiley = get_tile_at_pixel(mousex, mousey)
        if tilex != None and tiley != None:
            if not revealed_tiles[tilex][tiley]:
                draw_highlight_tile(tilex, tiley)
            if not revealed_tiles[tilex][tiley] and mouse_clicked:
                reveal_tile_animation(main_board, [(tilex, tiley)])
                revealed_tiles[tilex][tiley] = True
                counter.append((tilex, tiley))
                
        pygame.display.update()
        FPSCLOCK.tick(FPS)


def generate_default_tiles(default_value):
    '''
    returns list of 12 x 12 tiles set to False
    '''
    default_tiles = []
    for i in range(BOARDWIDTH):
        default_tiles.append([default_value] * BOARDHEIGHT)
    return default_tiles

    
def reveal_tile_animation(board, tile_to_reveal):
    '''
    board: list of board tiles
    tile_to_reveal: tuple of tile coords to apply the reveal animation to
    '''
    for coverage in range(TILESIZE, (-REVEALSPEED) - 1, -REVEALSPEED):
        draw_tile_covers(board, tile_to_reveal, coverage)

        
def draw_tile_covers(board, tile, coverage):
    '''
    board: list of board tiles
    tile: tuple of tile coords to reveal
    coverage: int
    '''
    left, top = left_top_coords_tile(tile[0][0], tile[0][1])
    if board[tile[0][0]][tile[0][1]] != (None, None):
        pygame.draw.rect(DISPLAYSURF, SHIPCOLOR, (left, top, TILESIZE,
                                                  TILESIZE))
    else:
        pygame.draw.rect(DISPLAYSURF, BGCOLOR, (left, top, TILESIZE, 
                                                TILESIZE))
    if coverage > 0:
        pygame.draw.rect(DISPLAYSURF, TILECOLOR, (left, top, coverage, 
                                                  TILESIZE))
            
    pygame.display.update()
    FPSCLOCK.tick(FPS)
    

def check_for_quit():
    for event in pygame.event.get(QUIT):
        pygame.quit()
        sys.exit()


def draw_board(board, revealed):
    '''
    board: list of board tiles
    revealed: list of revealed tiles
    '''
    for tilex in range(BOARDWIDTH):
        for tiley in range(BOARDHEIGHT):
            left, top = left_top_coords_tile(tilex, tiley)
            if not revealed[tilex][tiley]:
                pygame.draw.rect(DISPLAYSURF, TILECOLOR, (left, top, TILESIZE,
                                                          TILESIZE))
            else:
                if board[tilex][tiley] != (None, None):
                    pygame.draw.rect(DISPLAYSURF, SHIPCOLOR, (left, top, 
                                     TILESIZE, TILESIZE))
                else:
                    pygame.draw.rect(DISPLAYSURF, BGCOLOR, (left, top, 
                                     TILESIZE, TILESIZE))
                
    for x in range(0, BOARDWIDTH * TILESIZE, TILESIZE):
        pygame.draw.line(DISPLAYSURF, DARKGRAY, (x + XMARGIN, YMARGIN), \
                        (x + XMARGIN, WINDOWHEIGHT - YMARGIN))
    for y in range(0, BOARDHEIGHT * TILESIZE, TILESIZE):
        pygame.draw.line(DISPLAYSURF, DARKGRAY, (XMARGIN, y + YMARGIN), \
                (WINDOWWIDTH - (DISPLAYWIDTH + 20 + XMARGIN), y + YMARGIN))


def make_ships():
    '''
    returns list of tuples of ships, each section of a ship has
    the tuple (ship name, shot)
    '''
    slist = []
    # make battleship
    ship = []
    for i in range(4):
        ship.append(('battleship',False))
    slist.append(ship)    
    # make destroyer
    ship = []
    for i in range(3):
        ship.append(('destroyer',False))
    slist.append(ship)
    # make submarine
    ship = []
    for i in range(3):
        ship.append(('submarine',False))
    slist.append(ship)
    
    return slist
                

def add_ships_to_board(board, ships):
    '''
    return list of board tiles with ships placed on certain tiles
    board: list of board tiles
    ships: list of ships (name, bool) to place on board
    '''
    new_board = board[:]
    for ship in ships:
        for i in range(len(ship)):
            if ship[i][0] == 'battleship':
                new_board[1][1+i] = ship[i]
            elif ship[i][0] == 'destroyer':
                new_board[3][2+i] = ship[i]
            elif ship[i][0] == 'submarine':
                new_board[3+i][8] = ship[i]
    return new_board

        
def left_top_coords_tile(tilex, tiley):
    '''
    returns left and top pixel coords
    tilex: int
    tiley: int
    return: tuple (int, int)
    '''
    left = tilex * TILESIZE + XMARGIN
    top = tiley * TILESIZE + YMARGIN
    return (left, top)
    
    
def get_tile_at_pixel(x, y):
    '''
    returns tile coordinates of pixel at top left, defaults to (None, None)
    x: int
    y: int
    return: tuple (tilex, tiley)
    '''
    for tilex in range(BOARDWIDTH):
        for tiley in range(BOARDHEIGHT):
            left, top = left_top_coords_tile(tilex, tiley)
            tile_rect = pygame.Rect(left, top, TILESIZE, TILESIZE)
            if tile_rect.collidepoint(x, y):
                return (tilex, tiley)
    return (None, None)
    
    
def draw_highlight_tile(tilex, tiley):
    '''
    tilex: int
    tiley: int
    '''
    left, top = left_top_coords_tile(tilex, tiley)
    pygame.draw.rect(DISPLAYSURF, HIGHLIGHTCOLOR,
                    (left, top, TILESIZE, TILESIZE), 4)


def show_help_screen():
    # display the help screen until a button is pressed
    line1_surf, line1_rect = make_text_objs('Press a key to return to the game', 
                                            BASICFONT, TEXTCOLOR)
    line1_rect.topleft = (TEXT_LEFT_POSN, TEXT_HEIGHT)
    DISPLAYSURF.blit(line1_surf, line1_rect)
    
    line2_surf, line2_rect = make_text_objs('This is the classic game of ' \
                                            'battleship. Your objective is ' \
                                            'to sink as many ships', 
                                            BASICFONT, TEXTCOLOR)
    line2_rect.topleft = (TEXT_LEFT_POSN, TEXT_HEIGHT * 3)
    DISPLAYSURF.blit(line2_surf, line2_rect)

    line3_surf, line3_rect = make_text_objs('as possible using only 20 shots.', 
                                            BASICFONT, TEXTCOLOR)
    line3_rect.topleft = (TEXT_LEFT_POSN, TEXT_HEIGHT * 4)
    DISPLAYSURF.blit(line3_surf, line3_rect)

    while check_for_keypress() == None:
        pygame.display.update()
        FPSCLOCK.tick()

        
def check_for_keypress():
    # pulling out all KEYDOWN and KEYUP events from queue and returning any 
    # KEYUP else return None
    for event in pygame.event.get([KEYDOWN, KEYUP]):
        if event.type == KEYDOWN:
            continue
        return event.key
    return None

    
def make_text_objs(text, font, color):
    '''
    text: string
    font: Font object
    color: tuple of color (red, green blue)
    return: surface object, rectangle object
    '''
    surf = font.render(text, True, color)
    return surf, surf.get_rect()


def show_text_screen(text):
    '''
    text: string
    '''
    DISPLAYSURF.fill(BGCOLOR)
    titleSurf, titleRect = make_text_objs(text, BIGFONT, TEXTSHADOWCOLOR)
    titleRect.center = (int(WINDOWWIDTH / 2), int(WINDOWHEIGHT / 2))
    DISPLAYSURF.blit(titleSurf, titleRect)
    
    titleSurf, titleRect = make_text_objs(text, BIGFONT, TEXTCOLOR)
    titleRect.center = (int(WINDOWWIDTH / 2) - 3, int(WINDOWHEIGHT / 2) - 3)
    DISPLAYSURF.blit(titleSurf, titleRect)
    
    pressKeySurf, pressKeyRect = make_text_objs('Press a key to play.', 
                                                BASICFONT, TEXTCOLOR)
    pressKeyRect.center = (int(WINDOWWIDTH / 2), int(WINDOWHEIGHT / 2) + 100)
    DISPLAYSURF.blit(pressKeySurf, pressKeyRect)
    
    while check_for_keypress() == None:
        pygame.display.update()
        FPSCLOCK.tick()    

        
    
if __name__ == "__main__": #This calls the game loop
    main()

You should modularize and generalize things in python, a little bit more in your case can make things allot easier latter on. For example, limit the number of functions that act as specific game commands or actions. Too many will make it harder to re-use or modify latter on.

Start by building an entity system, then on top of this a pipeline for loading and managing the entities with basic string commands.

Please use classes to do the entity system, do not use functions in a flat file. That way you can abstract allot of the game away.

Later when you need a function that can build ships, move them or find certain tiles; it can all be done through a single mother class.

If you do not understand any of the concepts or words I described above, then please either ask for clarification or google it.

Thank you for the feedback. I didn't understand all of your recommendations and will Google it as you suggested. I do have a couple of questions to clarify however.

When you say 'limit the number of functions that act as specific game commands or actions' do you mean that functional programming is not recommended, or do you mean something else?

Is a 'single mother class' some sort of game class that I create an instance of for each game?

Let's first define what type of functional programming you mean. To me functional programming is a style of programming that treats the program flow like an equation void of any variables. I think you view it from the perspective of lets make a function that moves a ship forward and to the left. If you have a function for every possible game action, that will eventually become very hard to maintain.

The single mother class would be your game class. Inside of which is the game loop and support functions for interacting with the entity system.