pycallgraph : usage example

'pycallgraph' is a fine python utility enabling developers to prepare call graph for any python code piece... it also notifies the number of times a call being made and total time spent in it

Homepage: http://pycallgraph.slowchop.com/pycallgraph/wiki
Codebase: https://github.com/gak/pycallgraph

it require 'graphviz' (http://www.graphviz.org/) to be present on the same machine for image generation from the analyzed calls data...

install : $ pip install pycallgraph

Usage#1 Selective graphing

wrap the code to be graphed as follows...

import pycallgraph
pycallgraph.start_trace()
fetch() # logic to be graphed
pycallgraph.stop_trace()
just_log() # logic NOT to be graphed
pycallgraph.start_trace()
process() # logic to be graphed
pycallgraph.stop_trace()
pycallgraph.make_dot_graph('path_to_graph.png')

Usage#2 Decorator

Import the decorator method and place the decorator over any method where call graph is required...
import this file wherever you require the @callgraph decorator and use it

Decorator Python code. Sample code with decorator usage and selective trace usage are at end of this blog... from this gist: https://gist.github.com/abhishekkr/5592520



pycallgraph.start_trace() method lets you pass a filter function to not graph some modules on purpose, say in nova I don't wanna graph all the dependency libraries magical calls...


STATUTORY WARNING: Graph will be huge for a very high level call and probably unreadable due to overworked image generator. Use it wisely on burnt areas.


Call Graph images for code sample in Gists

for call with decorator



for call with selective trace

console and json

recently Alan posted a very nice aticle around prettifying json, reminded me of <this draft>... he posted 2 out of 3 utilities I was gonna mention... so here is 3rd and the shell profile way to use first 2

$ sudo wget -c -O /etc/profile.d/a.json.sh https://raw.github.com/abhishekkr/tux-svc-mux/master/shell_profile/a.json.sh

it contains 2 functions available at shell

# usage example:
# $ json_me 'echo {"a": 1, "b": 2}'
# $ json_me 'curl http://127.0.0.1/my.json'
json_me(){
bash -c $@ | python -mjson.tool
}

# requirement: $ pip install pjson
# usage example:
# $ pjson_me 'echo {"a": 1, "b": 2}'
# $ pjson_me 'curl http://127.0.0.1/my.json'
pjson_me(){
bash -c $@ | pjson
}

3rd utility is 'jq', an awesome utility which prettifies an perform sed-like operations on json. This tutorial describes all its magical powers.