Python equivalent to Bash comand “echo”?

Question

I am trying to trying to control the GPIOs on my RPi with Python but without one of those modules that require root permissions to be used. I found that trivial way of just "echoing" 1 or 0 to the value file of the GPIO through the console. I also wrote a Python script doing this automatically. So far so good. But this only works if the file (in this case: /sys/class/gpio/gpio17) already exists. I could easily create this folder everytime after booting the Pi, through the console like this:

pi@raspberrypi ~ $ cd /sys/class/gpio
pi@raspberrypi /sys/class/gpio $ echo "17" > export

After this I will have the folder /sys/class/gpio/gpio17 in which I find the information about the pin and can modify it.

So basically my question is: How would I incorporate this step into my Python script. Is there a way to move to the directory and export this folder using Python? I figured it out using a seperate Bash script whitch I then run inside my Python script, but I'd like to avoid using several languages and was wondering if there was an equivalent to the "echo" comand in Python. I searched for some days now but couldn't find anything. If there is, a link would be highly appreciated as well!

Thank You in advance,

a newbie

Answer 1

From your description you should simply need to write the required number to the file named /sys/class/gpio/export .

GPIO_EXPORT = '/sys/class/gpio/export'
PIN = 17
with open(GPIO_EXPORT, 'w') as export:
    export.write(str(PIN))

Answer 2

there a re a lot of options. you can directly use bash syntax in your python code with os module (or more flexible - subprocess module).

start python interpreter in your working directory and,

>>> import os
>>> os.system("echo 18>import")
0
>>> exit()
$ ls -a
.  ..  import
$ cat import
18

or write file.

>>> with open("newport", "w") as newport:
...     newport.write("19")
... 
>>> exit()
$ ls -a
.  ..  import  newport
$ cat newport 
19

and so on. have a look up to original documentation