CODEWITHSUNDEEP
pythonlinuxbashparsingloops
Tolga Varol
Tolga Varol

Reputation: 1236

Running a Bash Command in a loop in a Python Script

I have this script of mine and it is for modifying some data I gather from GPS module. I run this code but it says there is a syntax error and I couldn't understand why there is an error, normally I use that bash command for parsing, can't it be used in a Python loop?

**

import serial
import struct
ser = serial.Serial("/dev/ttyUSB0", 4800, timeout = 1)
file = open("/home/pi/GPSWIFI.csv", "w")
file.write('\n')
for i in range(0,5):
       val = ser.readline();
       print >> file ,i,',',val
       cat /home/pi/GPSWIFI.csv | grep GPGGA | cut -c19-42 >GPSWIFIMODIFIED.csv
file.close()

**

Thanks in advance.

Upvotes: 2

Views: 4209

Answers (1)

Arusekk
Arusekk

Reputation: 881

running bash commands in python can be done using os.system function, or, more recommended, through subprocess.Popen. You can find more info here:

https://docs.python.org/2/library/subprocess.html#popen-constructor

It would be better if you used python-specific implementation instead, like this:

import serial
ser = serial.Serial("/dev/ttyUSB0", 4800, timeout = 1)
file = open("/home/pi/GPSWIFIMODIFIED.csv", "w")
file.write('\n')
for i in range(0,5):
       val = ser.readline();
       if val.find("GPGGA")==-1: continue
       print >> file ,i,',',val[18:42]
file.close()

note that slice in python (this val[18:42]) is indexed from 0

Upvotes: 2

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