Question

我正在尝试用Python编写一个具有特殊性的开关。

OperativeSystems = {"nt": os.system("cls"), "posix": os.system("clear")}
try:
    OperativeSystems[os.name]
except:
    print("Can not clean the screen in the current operating system")

我想执行命令清除控制台，但我的程序执行“cls”和“clear”。这是我的问题。

谢谢。

Answer 1

OperativeSystems = {"nt": os.system("cls"), "posix": os.system("clear")}

在运行时声明字典时，您正在调用os.system。你可能想要这样做

OperativeSystems = {"nt": lambda: os.system("cls"), "posix": lambda: os.system("clear")}

OperativeSystems["nt"]()

现在进行查找会返回一个lambda（快捷方式函数），调用时会调用os.system

Answer 2

您正在第一行执行两个os.system()调用，实际存储在字典中的是os.system()调用的返回值。要么只将参数存储到字典中的os.system()并在os.system(OperativeSystems[os.name])内调用try，要么将字典值变为lambdas。

Answer 3

## First solution

class OperatingSystem:
    OSDict = {
        "nt" : NTOs,
        "posix" : PosixOs
        }
    @staticmethod
    def create_os(self,name):
        return self.OSDict[name]()

class NTos:
    def clear_screen(self):
        os.system("cls")

class PosixOs:
    def clear_screen(self):
        os.system("clear")

OperatingSystem.create_os("nt").clear_screen()
OperatingSystem.create_os("posix").clear_screen()

## Second solution

def clear(os_name):
    if os_name == "nt":
        command = "cls"
    if os_name == "posix":
        command = "clear"
    os.system(command)

clear("nt")
clear("posix")


## Third solution

OperatingSystems = {
    "nt"    : "cls",
    "posix" : "clear"
    }

os.system(OpeartingSystems("nt"))
os.system(OpeartingSystems("posix"))

## Fourth solution

# This is screaming for polymorphisme (solution #1)
OperatingSystems = {
    "nt"    : {"clear_screen":lambda : os.system("cls")}
    "posix" : {"clear_screen":lambda : os.system("clear")}
    }

OperatingSystems["nt"].clear_screen()

错误“切换”+特殊性 - Python

3 个答案: