python迭代循环与用户输入详解

FOR(iteration) 循环

for循环是Python中最常用的迭代机制。几乎 Python 中的任何结构都可以通过 for 进行迭代。包括列表、元组、字典等。另一个常见的循环是 while 循环，但 for 循环将是你最常看到的循环。

什么是 while 循环

while 循环会判断一个初始条件。如果条件为真，它将执行迭代。每次迭代后，都会重新判断条件。如果为真，则继续迭代，否则退出循环。

通用语法

# 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。

while 循环中包含条件判断。

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。

示例

# 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.")

用户输入

在 Python 中，你可以使用 input() 函数来接受用户输入。该函数可以接受提示消息并等待用户输入。

通用用法

# Get some input from the user.
variable = input('Please enter a value: ')
# Do something with the value that was entered.

示例

以下示例提示用户输入姓名并将其添加到姓名列表中。

# 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)