Python 无法打印全局变量
调用函数后,我无法打印最终语句。我在这里尝试过其他解决方案,但似乎无法使Python 无法打印全局变量,python,scope,global,Python,Scope,Global,调用函数后,我无法打印最终语句。我在这里尝试过其他解决方案,但似乎无法使读取大小/时钟速率真正全球化 def get_config(): global clock_rate global read_size role = input("Will the Sync Link be used as downlink or uplink? Type \"downlink\" "for downlink,
读取大小
/时钟速率
真正全球化
def get_config():
global clock_rate
global read_size
role = input("Will the Sync Link be used as downlink or uplink? Type \"downlink\"
"for downlink, \"uplink\" for uplink: ")
if role == "downlink":
clock_rate = 10240 # Convolutional encoding always disabled when sending to EDU
print("Configured for downlink mode... Clock rate =",clock_rate,"bits per second.")
if role == "uplink":
CE_enabled = input("Is convolutional encoding enabled on the EDU? "
"1 is enabled, 0 is disabled: ")
if CE_enabled == 1:
read_size = 512 # When convolutional encoding is enabled, the EDU receives
# a 512 byte CADU frame.
print(read_size)
clock_rate = 20480
if CE_enabled == 0:
read_size = 256 # When convolutional encoding is disabled, the EDU receives
# a 256 byte CADU frame.
clock_rate = 10240
else:
print("Invalid input")
get_config()
print("Initiating transmit/receive... Read size =", read_size,
"bytes. Clock rate =", clock_rate, "bits per second.")
即使忽略对全局变量的依赖,您也没有在所有可能的情况下定义
时钟速率
和读取大小
。执行以下操作:
def get_config():
clock_rate = None
read_size = None
role = input("Role?")
if role == "uplink":
clock_rate = 10240
elif role == "downlink":
ce_enabled = input("Convolutional encoding enabled?")
if ce_enabled == "0":
read_size = 256
clock_rate = 10240
elif ce_enabled == "1":
read_size = 512
clock_rate = 20480
else:
raise ValueError("Invalid response for convolutional encoding")
else:
raise ValueError("Invalid role")
return clock_rate, read_size
clock_rate, read_size = get_config()
print("Initiating transmit/receive... Read size =",read_size,"bytes. Clock rate =",clock_rate,"bits per second.")
您可以为每个变量提供默认值(以前指定的
None
)而不是在每种情况下都引发错误。我将把它作为一个答案而不是注释,以防止出现任何混淆。要使用全局变量,您不必在全局范围内初始化它们。以下代码将完美地工作:
def some_function():
global some_global
some_global = "Hello, world!"
some_function()
print(some_global)
全局变量不必在外部范围内初始化。相反,它们可以在任何时间在任何范围内定义。唯一的限制是:在访问它们之前必须定义它们。这就是你的代码的问题所在
在“下行链路”模式下,您的函数不定义
read_size
,在“上行链路”模式下,您将输入与0
和1
进行比较,它们是整数,因此这些表达式永远不会产生True
。这意味着,到达告诉用户输入无效的else
块。在这种情况下,无论是read\u size
还是clock\u rate
都不会在最终打印语句之前定义。在使用全局关键字修改其范围之前,您需要声明clock rate和read\u size变量,以便更改它们
您还需要一个elif CE_enabled==0,否则如果您输入1,您总是会得到无效的输入
见下文:
clock_rate=None
read_size = None
def get_config():
global clock_rate
global read_size
role = input("Will the Sync Link be used as downlink or uplink? Type \"downlink\" for downlink, \"uplink\" for uplink: ")
if role == "downlink":
clock_rate = 10240 # Convolutional encoding always disabled when sending to EDU
print("Configured for downlink mode... Clock rate =",clock_rate,"bits per second.")
if role == "uplink":
CE_enabled = int(input("Is convolutional encoding enabled on the EDU? 1 is enabled, 0 is disabled: "))
if CE_enabled == 1:
read_size = 512 # When convolutional encoding is enabled, the EDU receives a 512 byte CADU frame
print("Read size:", read_size)
clock_rate = 20480
elif CE_enabled == 0:
read_size = 256 # When convolutional encoding is disabled, the EDU receives a 256 byte CADU frame
clock_rate = 10240
else:
print("Invalid input")
get_config()
print("Initiating transmit/receive... Read size =",read_size,"bytes. Clock rate =",clock_rate,"bits per second.")
您需要在函数范围之外定义
clock\u rate
和read\u size
。为什么不让函数返回read\u size
和clock\u rate
呢?我已经尝试在函数之外定义变量,但我仍然无法让read\u size工作。我可以这样做,但这需要我重写更多的函数。我强烈建议重写更多的函数。函数的执行可能会也可能不会为这两个变量赋值——因此,如果要在调用后引用它们的值,则需要确保它们存在,并且在调用之前具有一些默认值它。这根本不是真的,看我的答案。谢谢你,我用了这个,它成功了。对于您的原始代码,我使用的API有一个错误,但在将clock_rate=None和read_size=None放入get_config()后,我修复了它。非常感谢你的帮助。