Why doesn't my Python Function start when called upon?

Whenever I'm calling my start() function, after it's been declared, I get a error saying it doesn't exist. My complete code is below.

import random
import time
global monsters
monsters = ['Goblin','Orc','Knight','Unicorn','Black Bear','White Dragon','Black Dragon','Dark Knight','Undead Corpse']
global player_level
player_level = 1
global player_exp
global monster_level
monster_level = monster_determ_easy
player_exp = 0
player_exp_n = 10
global monster_attack
global player_attack
p开发者_如何转开发layer_attack = random.randint(1,4) + player_level
global monster_levels
global monster_determ_easy
global monster_determ_medium
global monster_determ_hard
global monster_determ_epic
global attacks
global gold
gold = 0
attacks = ['Punch','Fireball']
monster_determ_easy = random.randint(1,3)
monster_levels_easy = player_level - monster_determ_easy

monster_determ_medium = random.randint(1,3)
monster_levels_medium = player_level + monster_determ_medium

monster_determ_hard = random.randint(3,5)
monster_levels_hard = player_level + monster_determ_hard

monster_determ_epic = random.randint(5,10)
monster_levels_epic = player_level + monster_determ_epic

monster_attack = monsters_levels + random.randint(1,3)

def start():
    if player_exp>=player_exp_n:
            player_level=player_level+1
            print "You've reached level ",player_level
            gold=gold+random.randint(1,15) + player_level
            print 'You were awared ',' gold!'
            start()
            command = raw_input(">")
    if command == "fight":
            player_attack = random.randint(1,4) + player_level
            monster_attack = monsters_levels + random.randint(1,3)
            choose_monster = random.choose(monsters)
            print 'You encounter a level ',monster_determ_easy,choose_monster,'.'
            time.sleep(1)
            print 'Prepare to fight!'
            strike = random.random()
            if strike>=0.5:
                if player_attack >= monster_attack:
                    print 'You slained the ',choose_monster,'!'
                    exp_choose = random.randint(1,5) + player_level
                    player_exp = player_exp + exp_choose
                    print 'You were awarded ',exp_choose,' XP!'
                    start()

start()
# This was just added

Because the first if statement evaluates to false, so you never have the opportunity to set the command variable.

Because it's only called from within itself.