Counting string occurrences in Python

You should just try to google for your subject line. The second hit gave me this:

Great - and it seems it's a JSON encoded string so rather than doing any string processing on it why not decode it using the json module (loads method) which will turn it into a list of dicts which you can loop through something roughly like this.

import json

sats = json.loads(gps_str) total_sats = len(sats) used_sats = 0 for sat in sats: if sat['used']: used_sats = used_sats + 1

Thanks, Stefan. I had searched, and tried a function such as you suggest, but unfortunately it returned 0 when searching for either "used" or "True". There were no compiler errors, but I don't know Python well enough to know where I'm going wrong.

On 10/04/2016 11:15, Ahem A Rivet's Shot wrote: []

Thanks, Ahem, I appreciate your help. I did try that but it seems not to work for my data at least. Here's the error message and the program:

Traceback (most recent call last): File "gpsdRead.py", line 22, in sats = json.loads (report.satellites) File "/usr/lib/python2.7/json/__init__.py", line 338, in loads return _default_decoder.decode(s) File "/usr/lib/python2.7/json/decoder.py", line 366, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) TypeError: expected string or buffer ===========================

import gps import json from collections import Counter

# Listen on port 2947 (gpsd) of localhost session = gps.gps("localhost", "2947") session.stream(gps.WATCH_ENABLE | gps.WATCH_NEWSTYLE)

while True: try: report = session.next() # Wait for a 'SKY' report and display the current time # To see all report data, uncomment the line below # print report if report['class'] == 'SKY': # print report session = None if hasattr(report, 'satellites'): # print report.satellites # print report.satellites.count("used") # print report.satellites.count("True") sats = json.loads (report.satellites) total_sats = len (sats) used_sats = 0 for sat in sats: if sat['used']: used_sats = used_sats + 1 print total_sats print used_sats session = None quit() except KeyError: pass except KeyboardInterrupt: quit() except StopIteration: session = None print "GPSD has terminated"

Show us the code you wrote, then we *might* have some chance of suggesting what's wrong.

(... and Python isn't a compiler)

On Sun, 10 Apr 2016 15:17:37 +0100, David Taylor declaimed the following:

From your earlier post:

How did you produce that "report". I'm not up on JSON myself, but those structures don't seem valid. With them in place I get

ValueError: No JSON object could be decoded

Removing them got me to

ValueError: Expecting property name: line 2 column 3 (char 3)

After much trial and error I managed to get

report = """ [ {"ss": 24, "el": 10, "PRN": 67, "az": 130, "used":"False"}, {"ss": 30, "el": 63, "PRN": 68, "az": 130, "used":"False"}, {"ss": 14, "el": 59, "PRN": 69, "az": 309, "used":"False"}, {"ss": 12, "el": 73, "PRN": 78, "az": 118, "used": "False"}, {"ss": 26, "el": 39, "PRN": 79, "az": 190, "used":"False"}, {"ss": 17, "el": 18, "PRN": 85, "az": 315, "used":"False"}, {"ss": 31, "el": 26, "PRN": 136, "az": 170, "used":"True"}, {"ss": 30, "el": 23, "PRN": 28, "az": 137, "used": "True"}, {"ss": 38, "el": 66, "PRN": 30, "az": 92, "used":"True"}, {"ss": 31, "el": 40, "PRN": 20, "az": 297, "used":"True"}, {"ss": 27, "el": 15, "PRN": 21, "az": 327, "used":"True"}, {"ss": 11, "el": 8, "PRN": 27, "az": 23, "used":"False"}, {"ss": 32, "el": 66, "PRN": 5, "az": 212, "used": "True"}, {"ss": 27, "el": 40, "PRN": 7, "az": 61, "used": "True"}, {"ss": 17, "el": 4, "PRN": 9, "az": 96, "used":"False"}, {"ss": 38, "el": 54, "PRN": 13, "az": 269, "used":"True"} ] """ to feed to the loader. The order has changed as I was cut&pasting from one record up to the full set. Note that I had to:

How you massage your input data to fit is another matter...

-=-=-=-=- import json

report = """ [ {"ss": 24, "el": 10, "PRN": 67, "az": 130, "used":"False"}, {"ss": 30, "el": 63, "PRN": 68, "az": 130, "used":"False"}, {"ss": 14, "el": 59, "PRN": 69, "az": 309, "used":"False"}, {"ss": 12, "el": 73, "PRN": 78, "az": 118, "used": "False"}, {"ss": 26, "el": 39, "PRN": 79, "az": 190, "used":"False"}, {"ss": 17, "el": 18, "PRN": 85, "az": 315, "used":"False"}, {"ss": 31, "el": 26, "PRN": 136, "az": 170, "used":"True"}, {"ss": 30, "el": 23, "PRN": 28, "az": 137, "used": "True"}, {"ss": 38, "el": 66, "PRN": 30, "az": 92, "used":"True"}, {"ss": 31, "el": 40, "PRN": 20, "az": 297, "used":"True"}, {"ss": 27, "el": 15, "PRN": 21, "az": 327, "used":"True"}, {"ss": 11, "el": 8, "PRN": 27, "az": 23, "used":"False"}, {"ss": 32, "el": 66, "PRN": 5, "az": 212, "used": "True"}, {"ss": 27, "el": 40, "PRN": 7, "az": 61, "used": "True"}, {"ss": 17, "el": 4, "PRN": 9, "az": 96, "used":"False"}, {"ss": 38, "el": 54, "PRN": 13, "az": 269, "used":"True"} ] """

result = json.loads(report) print "Reported PRNs: ", len(result) print "Visible PRNs: ", len([rec for rec in result if rec[u"used"] == u"True"])

-=-=-=-=-=-

Reported PRNs: 16 Visible PRNs: 8

There are newsgroups for python too, which should be used in preference unless your problem is specific to the Raspberry Pi, which in this case it isn't.

---druck

You're right, of course, about the newsgroups, although in this case the issues /may/ be RPi-specific since it has not got the up-to-date versions of gpsd. I'm more tending towards writing my own program in Pascal (Lazarus) as the delay in getting the required message (SKY) is annoying me!

Ah I see it's already structured and what you posted was the result of python turning it into a string to print it - then I was trying to get you to turn it back into what you started with :)

Life is simpler for you. Ignore this bit:

In here use report.satellites where I have sats.

Or you can use the more compact way of counting suggested by Dennis - I wouldn't because it allocates an array that isn't used for anything but counting it's length.

One more thing this:

Would be nicer as:

if 'satellites' in report:

Yes, comp.lang.python is a very friendly and helpful newsgroup.

Thanks for that, Steve. It's now written up here:

and your help is acknowledged. If anyone else feels they should be acknowledged please let me know.

Thanks for everyone's help with this. Whilst I did get a working solution with Python, I found a much quick way was to write a small piece of C. For those interested, please see: