CODEWITHSUNDEEP
pythonscopeglobal
mxGlass
mxGlass

Reputation: 13

Not able to print global variables

I am not able to print the final statement after the function is called. I have tried other solutions from here, but can't seem to get read_size/clock_rate to be truly global.

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.")

Upvotes: 0

Views: 84

Answers (3)

cannonfodda
cannonfodda

Reputation: 76

You will need to declare the clock rate and read_size variables before you modify their scope with the global keyword so you can change them.

You also need an elif CE_enabled==0 otherwise you always get invalid input if you input 1.

See below:

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.")

Upvotes: 0

Koen
Koen

Reputation: 155

I am going to put this as an answer instead of a comment to stop any confusion from happening. To use global variables, you do NOT have to have initialized them in the global scope. The following code will work perfectly:

def some_function():
    global some_global
    some_global = "Hello, world!"

some_function()
print(some_global)

Globals do not have to be initialized in the outer scope. Instead, they can be defined in any scope at any time. The only constraint is: they must be defined before accessed. This is what's wrong with your code.

In the 'downlink' mode, your function does not define read_size and in the 'uplink' mode, you are comparing the input against 0 and 1, which are integers and therefore those expressions will never result in True. This means, the else block is reached that tells the user the input is invalid. In this case, neither read_size nor clock_rate will be defined before the final print statement.

Upvotes: 0

chepner
chepner

Reputation: 531215

Even ignoring the dependence on global variables, you aren't defining clock_rate and read_size in all possible cases. Do something like the following:

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.")

Instead of raising an error in each case, you could provide default values (other than the previously assigned None) to each variable.

Upvotes: 1

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