If...Else

1 _username = "A1_Code" 2 _password = "123" 3  4 username = input("username:") 5 password = input("password:") 6  7 if _username == username and _password == password: 8     print("Welcome user {name} login...".format(name=username)) 9 else:10     print("Invalid username or password!")

　　If...Elif...Else

1 age_of_oldboy = 562 guess_age = int(input("guess age:"))3 4 if guess_age == age_of_oldboy:5     print("yes,you got it.")6 elif guess_age > age_of_oldboy:7     print("think smaller...")8 else:9     print("think bigger!")

 　　while

1 count = 02 while True:3     print("count:", count)4     count = count + 1 #count+=1

　　Break 跳出循环

1 count = 02 while True:3     print("count:", count)4     count = count + 1 #count+=15     if count == 1000:6         break

　　加计数器

1 age_of_oldboy = 56 2  3 count = 0 4 while True: 5     if count == 3: 6         break 7     guess_age = int(input("guess age:")) 8     if guess_age == age_of_oldboy: 9         print("yes,you got it.")10         break11     elif guess_age > age_of_oldboy:12         print("think smaller...")13     else:14         print("think bigger!")15 16     count += 1

　While 后加条件

1 age_of_oldboy = 56 2  3 count = 0 4 while count < 3: 5     if count == 3: 6         break 7     guess_age = int(input("guess age:")) 8     if guess_age == age_of_oldboy: 9         print("yes,you got it.")10         break11     elif guess_age > age_of_oldboy:12         print("think smaller...")13     else:14         print("think bigger!")15 16     count += 1

 　　While...Else

1 age_of_oldboy = 56 2  3 count = 0 4 while count < 3: 5     if count == 3: 6         break 7     guess_age = int(input("guess age:")) 8     if guess_age == age_of_oldboy: 9         print("yes,you got it.")10         break11     elif guess_age > age_of_oldboy:12         print("think smaller...")13     else:14         print("think bigger!")15     count += 116 else:17     print("you have tried too many times...fuck off")

 　　For

1 for i in range(10):2     print("loop", i)

　　For...Else

1 age_of_oldboy = 56 2  3 for i in range(3): 4     guess_age = int(input("guess age:")) 5     if guess_age == age_of_oldboy: 6         print("yes,you got it.") 7         break 8     elif guess_age > age_of_oldboy: 9         print("think smaller...")10     else:11         print("think bigger!")12 else:13     print("you have tried too many times...fuck off")

 　　For 跳跃循环

1 for i in range(0, 10, 2):2     print("loop", i)

　　优化

1 age_of_oldboy = 56 2  3 count = 0 4 while count < 3: 5     if count == 3: 6         break 7     guess_age = int(input("guess age:")) 8     if guess_age == age_of_oldboy: 9         print("yes,you got it.")10         break11     elif guess_age > age_of_oldboy:12         print("think smaller...")13     else:14         print("think bigger!")15     count += 116     if count == 3:17         countine_confirm = input("Do you want to keep guessing..?")18         if countine_confirm != 'n':19             count = 0

　　加断点 Debug

　　Continue 跳出本次循环，继续下次循环；Break　结束循环

1 for i in range(0, 10):2     if i < 3:3         print("loop", i)4     else:5         continue6     print("hehe...")

 　　循环套循环

1 for i in range(10):2     print('----------', i)3     for j in range(10):4         print(j)5         if j > 5:6             break