Setting an occurrence percentage for a random.choice

I am writing a little baseball game to test while loops and the use of the random function.

Can I set an occurrence percentage for the variables in "pitches" i.e. 'fastball' is thrown 50% of the time and 'curve' is thrown 30% of the time and so on? I still want it to select them from random but want it to take the percentage in to account.

I have been coding for all but 2 weeks so go easy on my code please. Thanks.

import random import os import sys

pitches = ['fastball', 'curve', 'changeup'] call = ['ball', 'strike'] balls = 0 strikes = 0 pitch_count = 0

def next_batter(): nextBatter = input("Would you like to play another batter? Y/n ").lower() if nextBatter != 'n': pitchAgain() else: sys.exit()

def welcome(): start = input("would you like to send your batter to the plate? Y/n") if start == 'n': print("BYE!") sys.exit() else: return True

def pitchAgain(): balls = 2 strikes = 1 count = 1

while True:
    thrown = random.choice(pitches)
    print ("Pitch number {} was a {}".format(count,thrown))
    count +=1
    umpire = random.choice(call)
    if umpire == "ball":
        print("umpire called it a ball")
        print("The count is {} balls and {} strikes".format(balls,strikes))
        balls += 1
    else:
        print("umpire called it a Strike")
        strikes += 1
        print("The count is {} balls and {} strikes".format(balls,strikes))
    if count == 5:
        print("you need a new pitcher")
        sys.exit()

    if balls == 3 and strikes == 2:
        print("Full Count")
    elif balls >= 4:
        print("walked the batter")
        next_batter()
    elif strikes >= 3:
        print("Stuck him out!")
        next_batter()

while True: welcome() pitchAgain()