for 循环是 Python 中最常用的迭代机制。Python 中几乎所有的结构都能被 for 迭代。包括列表，元组，字典等。另一种常用的循环是 while 循环，但是 for 循环会是你最常见到的循环。
什么是 while 循环
# Set an initial condition. game_active = True # Set up the while loop. while game_active: # Run the game. # At some point, the game ends and game_active will be set to False. # When that happens, the loop will stop executing. # Do anything else you want done after the loop runs.
每次循环前都要初始化一条判断为 true 的条件。
条件判断为 true 则执行循环内代码，不断迭代，判断。
判断为 false 则退出循环。
# The player's power starts out at 5. power = 5 # The player is allowed to keep playing as long as their power is over 0. while power > 0: print("You are still playing, because your power is %d." % power) # Your game code would go here, which includes challenges that make it # possible to lose power. # We can represent that by just taking away from the power. power = power - 1 print("\nOh no, your power dropped to 0! Game Over.")
在 Python 中你可以利用 input() 函数接受用户输入。函数可以接受一条提示信息，等待用户输入。
# Get some input from the user. variable = input('Please enter a value: ') # Do something with the value that was entered.
# Start with a list containing several names. names = ['guido', 'tim', 'jesse'] # Ask the user for a name. new_name = input("Please tell me someone I should know: ") # Add the new name to our list. names.append(new_name) # Show that the name has been added to the list. print(names)