Python How to Return value in while loop

Question

When put return in while loop the loop will stop How to fix it?

ser = serial.Serial(
    port='COM5',
    baudrate = 9600,
    timeout=1)
while 1:
    x=str(ser.readline())
    x = re.findall("\d+\.\d+", x)
    x = float(x[0])
    return(x) #loop stopped
    print(x)

Could you please help me?

Depends on what you want the loop to do instead. Have you tried [`yield`](http://stackoverflow.com/q/231767/1639625)? — tobias_k, Jan 13 '17 at 11:04
Perhaps you want a [generator](https://wiki.python.org/moin/Generators)? — Phylogenesis, Jan 13 '17 at 11:06
Thank you for your comment. I did not try yield yet but my project need to collecting 24 hours is it possible to collect huge data in yield? and i want to send data in realtime — Juizy J., Jan 13 '17 at 11:06
Yes i already put data in file but I want to show the output to digital display with QtPy too that why i want to return x to drive LCD Number at Qt — Juizy J., Jan 13 '17 at 11:14
Why use `return` at all? How about just updating the value in the display whilst you're in the `while` loop? — developius, Jan 13 '17 at 11:17
Just to clarify; you want to continuously read an input from `ser`, do some operations on it and then return it without breaking the continuous part of it? — Dillanm, Jan 13 '17 at 11:17

score 1 · Accepted Answer · answered Jan 13 '17 at 11:20

1

Simply take your

x=str(ser.readline())
x = re.findall("\d+\.\d+", x)
x = float(x[0])
return(x) #loop stopped

put it into a function like

def foo(ser):
    x=str(ser.readline())
    x = re.findall("\d+\.\d+", x)
    x = float(x[0])
    return(x)

and change your while loop to simply be

while 1:
    print(foo(ser))

However @developius had a better solution which would look something like

while 1:
    x=str(ser.readline())
    x = re.findall("\d+\.\d+", x)
    x = float(x[0])
    print(x)

answered Jan 13 '17 at 11:20

Dillanm

876
12
28

1

Thanks for advice Dillanm i will try i am a beginner of coding – Juizy J. Jan 13 '17 at 11:29
@JuizyJ. we all have to start somewhere! The Python docs are pretty good on their own, I also found [Codecademy](https://www.codecademy.com/learn/python) and [TutorialsPoint](https://www.tutorialspoint.com/python/) to be pretty good when I was learning Python, particularly Codecademy since it's interactive and gives immediate feedback! (and they're both free too!) – Dillanm Jan 13 '17 at 11:35

asif · Answer 2 · 2021-02-14T09:45:04.390

1

If you want to pass the values continuously to a separate piece of code, you can use yield.

You can modify your code as followed:

def func():
    while 1:
        x=str(ser.readline())
        x = re.findall("\d+\.\d+", x)
        x = float(x[0])
        yield x

And then call the function. Note that f will be a generator so you will have to loop over it as below.

f = func()
for i in f:
    print(i) # or use i for any purpose

Reference: here

edited Feb 14 '21 at 09:45

answered Feb 14 '21 at 08:04

asif

171
6

this worked ...!! i used for cv2.Vid while condition... <3<3 – Bharath Kumar Oct 07 '22 at 10:56

score -2 · Answer 3 · answered Jan 13 '17 at 11:43

-2

u can try this one

while 1:
    x=str(ser.readline())
    x = re.findall("\d+\.\d+", x)
    x = float(x[0])
return x

answered Jan 13 '17 at 11:43

Stefani Johnsson

381
1
5
18

Python How to Return value in while loop

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