if
你在生活中是不是经常遇到各种选择，比如玩色子，猜大小，比如走那条路回家。python程序中也会遇到这种情况，这就用到了 if 语句
_username = 'zou' _password = 'abc123' username = input("username:") password = input("password:") if _username == username and _password == password: print("Welcome user {name} login...".format(name=username)) else: print("Invalid username or password!")
money = int(input("请输入你兜里的钱:")) if money > 500: print("吃啤酒吃炸鸡. 生活美滋滋") elif money > 300: print("盖浇饭走起") elif money > 50: print("方便面走起") else: print("减肥走起")
while
在生活中，我们遇到过循环的事情吧？比如循环听歌，在程序中，循环也是存在的，
count=0 while True: print("count:",count) count=count+1
陷入了死循环，在实际项目中要避免出现死循环，True 的T必须是大写
age_of_oldboy = 56 while True: guess_age = int(input('guess age:')) if guess_age == age_of_oldboy: print("yes, you got it. ") elif guess_age > age_of_oldboy: print("think smaller...") else: print("thing bigger...")
一直可以输入，对或错都不结束
age_of_oldboy = 56 while True: guess_age = int(input('guess age:')) if guess_age == age_of_oldboy: print("yes, you got it. ") break elif guess_age > age_of_oldboy: print("think smaller...") else: print("thing bigger...")
加了个break，输入正确时退出
break 结束循环. 停止当前本层循环
age_of_oldboy = 56 count = 0 while count < 3: guess_age = int(input('guess age:')) if guess_age == age_of_oldboy: print("yes, you got it. ") break elif guess_age > age_of_oldboy: print("think smaller...") else: print("thing bigger...") count = count + 1
输错三次退出循环
age_of_oldboy = 56 count = 0 while count < 3: guess_age = int(input('guess age:')) if guess_age == age_of_oldboy: print("yes, you got it. ") break elif guess_age > age_of_oldboy: print("think smaller...") else: print("thing bigger...") count = count + 1 else: print("you have tried too many times...")
当程序正常执行完会执行最后一个else，如果中间遇到break，不执行else
while True: s = input("请开始说:") if s == 'q': break # 停止当前循环 # 过滤掉马化腾 if "马化腾" in s: # 在xxx中出现了xx print("你输入的内容非法. 不能输出") continue # 停止当前本次循环.继续执行下一次循环 print("喷的内容是:" + s)
count = 1 while count <= 10: print(count) count = count + 1 if count == 5: break # 彻底停止循环. 不会执行后面的else else: # while条件不成立的时候执行 print("这里是else")
continue：停止本次循环，继续执行下一次循环
