Python, use variable as object "name"

Question

I've been getting into Python for a while now, since I'm still a beginner, I try to keep things simple as much as possible. There is however one thing that I would like to be able to do, but cannot get right.

I've searched and found several questions that somewhat resemble, mine, but answers are mostly to use eval() and exec(), which I read is very bad practice. Using a dictionary seems to be another often proposed option, but I don't see how to apply this to my case.

class pthead:

    def __init__(self, name, port):
        self.name = name
        self.port = port

    def initialize(self):
            ser4.write(initialization_commands)  # works
            (self.port).write(initialization_commands)  # doesn't work


UART.setup("UART4")
ser4 = serial.Serial(port="/dev/ttyO4", baudrate=9600, timeout=0.5)

head = pthead("kop", "ser4")
head.initialize()

Is it really that hard to use the variable as an object (hope I get the terminology right)? I can hardly believe it is not a common thing to do, for example after user input...

I'm using python 2.7 (for legacy purposes).

Use this head = pthead("kop", ser4) it will work.

Rajan Chauhan
– Rajan Chauhan

2017-08-17 10:33:19 +00:00
Commented Aug 17, 2017 at 10:33 — Rajan Chauhan
– Rajan Chauhan, Commented Aug 17, 2017 at 10:33

Rajan Chauhan · Accepted Answer · 2017-08-17 12:25:03Z

1

You are not using it correctly. The port you are supplying isn't a port but a string `"ser4".

class pthead:

    def __init__(self, name, port):
        self.name = name
        self.port = port

    def initialize(self):
        self.port.write(initialization_commands)  # it will work

if __name__ == "__main__":
    UART.setup("UART4")
    ser4 = serial.Serial(port="/dev/ttyO4", baudrate=9600, timeout=0.5)

    head = pthead("kop", ser4) #supplying port as second argument
    head.initialize()

edited Aug 17, 2017 at 12:25

answered Aug 17, 2017 at 10:37

Rajan Chauhan

1,3831 gold badge15 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Dieter Vansteenwegen Over a year ago

That does indeed work when used in a script. In interactive mode (where I tried out different options), that wasn't the case... x = pthead("name", ser4) returns "NameError: name 'ser4' is not defined"

Rajan Chauhan Over a year ago

@DieterVansteenwegenON4DD If you are using it as a script then you need to provide a port value of ser4 there.Since you want to supply your provide port you need to define it before in the code then pass it as an argument.

Rajan Chauhan Over a year ago

The code outside the class is what you need to put in the other file while importing phead

Dieter Vansteenwegen Over a year ago

Maybe I wasn't clear in my reply. It does work when I run it as a script, but if I start interactive mode, then from foo import pthead and try to create an instance with x = pthead("name", ser4) I get the "NameError: name 'ser4' is not defined"error if I do not put quotes around the port.

Rajan Chauhan Over a year ago

@DieterVansteenwegenON4DD I got you but you haven't made your program like that you are supplying name and a port. You need to carryout changes either your __init__ function should take name and a port value as argument but here you are essentially using port variable as argument

|

Collectives™ on Stack Overflow

Python, use variable as object "name"

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related