How can I profile Python code line-by-line?

Question

I've been using cProfile to profile my code, and it's been working great. I also use gprof2dot.py to visualize the results (makes it a little clearer).

However, cProfile (and most other Python profilers I've seen so far) seem to only profile at the function-call level. This causes confusion when certain functions are called from different places - I have no idea if call #1 or call #2 is taking up the majority of the time. This gets even worse when the function in question is six levels deep, called from seven other places.

How do I get a line-by-line profiling?

Instead of this:

function #12, total time: 2.0s

I'd like to see something like this:

function #12 (called from somefile.py:102) 0.5s
function #12 (called from main.py:12) 1.5s

cProfile does show how much of the total time "transfers" to the parent, but again this connection is lost when you have a bunch of layers and interconnected calls.

Ideally, I'd love to have a GUI that would parse through the data, then show me my source file with a total time given to each line. Something like this:

main.py:

a = 1 # 0.0s
result = func(a) # 0.4s
c = 1000 # 0.0s
result = func(c) # 5.0s

Then I'd be able to click on the second "func(c)" call to see what's taking up time in that call, separate from the "func(a)" call. Does that make sense?

Answer 1

I believe that's what Robert Kern's line_profiler is intended for. From the link:

File: pystone.py
Function: Proc2 at line 149
Total time: 0.606656 s

Line #      Hits         Time  Per Hit   % Time  Line Contents
==============================================================
   149                                           @profile
   150                                           def Proc2(IntParIO):
   151     50000        82003      1.6     13.5      IntLoc = IntParIO + 10
   152     50000        63162      1.3     10.4      while 1:
   153     50000        69065      1.4     11.4          if Char1Glob == 'A':
   154     50000        66354      1.3     10.9              IntLoc = IntLoc - 1
   155     50000        67263      1.3     11.1              IntParIO = IntLoc - IntGlob
   156     50000        65494      1.3     10.8              EnumLoc = Ident1
   157     50000        68001      1.4     11.2          if EnumLoc == Ident1:
   158     50000        63739      1.3     10.5              break
   159     50000        61575      1.2     10.1      return IntParIO

Answer 2

You could also use pprofile(pypi). If you want to profile the entire execution, it does not require source code modification. You can also profile a subset of a larger program in two ways:

• toggle profiling when reaching a specific point in the code, such as:

  import pprofile
  profiler = pprofile.Profile()
  with profiler:
      some_code
  # Process profile content: generate a cachegrind file and send it to user.
  
  # You can also write the result to the console:
  profiler.print_stats()
  
  # Or to a file:
  profiler.dump_stats("/tmp/profiler_stats.txt")
  

• toggle profiling asynchronously from call stack (requires a way to trigger this code in considered application, for example a signal handler or an available worker thread) by using statistical profiling:

  import pprofile
  profiler = pprofile.StatisticalProfile()
  statistical_profiler_thread = pprofile.StatisticalThread(
      profiler=profiler,
  )
  with statistical_profiler_thread:
      sleep(n)
  # Likewise, process profile content
  

Code annotation output format is much like line profiler:

$ pprofile --threads 0 demo/threads.py
Command line: ['demo/threads.py']
Total duration: 1.00573s
File: demo/threads.py
File duration: 1.00168s (99.60%)
Line #|      Hits|         Time| Time per hit|      %|Source code
------+----------+-------------+-------------+-------+-----------
     1|         2|  3.21865e-05|  1.60933e-05|  0.00%|import threading
     2|         1|  5.96046e-06|  5.96046e-06|  0.00%|import time
     3|         0|            0|            0|  0.00%|
     4|         2|   1.5974e-05|  7.98702e-06|  0.00%|def func():
     5|         1|      1.00111|      1.00111| 99.54%|  time.sleep(1)
     6|         0|            0|            0|  0.00%|
     7|         2|  2.00272e-05|  1.00136e-05|  0.00%|def func2():
     8|         1|  1.69277e-05|  1.69277e-05|  0.00%|  pass
     9|         0|            0|            0|  0.00%|
    10|         1|  1.81198e-05|  1.81198e-05|  0.00%|t1 = threading.Thread(target=func)
(call)|         1|  0.000610828|  0.000610828|  0.06%|# /usr/lib/python2.7/threading.py:436 __init__
    11|         1|  1.52588e-05|  1.52588e-05|  0.00%|t2 = threading.Thread(target=func)
(call)|         1|  0.000438929|  0.000438929|  0.04%|# /usr/lib/python2.7/threading.py:436 __init__
    12|         1|  4.79221e-05|  4.79221e-05|  0.00%|t1.start()
(call)|         1|  0.000843048|  0.000843048|  0.08%|# /usr/lib/python2.7/threading.py:485 start
    13|         1|  6.48499e-05|  6.48499e-05|  0.01%|t2.start()
(call)|         1|   0.00115609|   0.00115609|  0.11%|# /usr/lib/python2.7/threading.py:485 start
    14|         1|  0.000205994|  0.000205994|  0.02%|(func(), func2())
(call)|         1|      1.00112|      1.00112| 99.54%|# demo/threads.py:4 func
(call)|         1|  3.09944e-05|  3.09944e-05|  0.00%|# demo/threads.py:7 func2
    15|         1|  7.62939e-05|  7.62939e-05|  0.01%|t1.join()
(call)|         1|  0.000423908|  0.000423908|  0.04%|# /usr/lib/python2.7/threading.py:653 join
    16|         1|  5.26905e-05|  5.26905e-05|  0.01%|t2.join()
(call)|         1|  0.000320196|  0.000320196|  0.03%|# /usr/lib/python2.7/threading.py:653 join

Note that because pprofile does not rely on code modification it can profile top-level module statements, allowing to profile program startup time (how long it takes to import modules, initialise globals, ...).

It can generate cachegrind-formatted output, so you can use kcachegrind to browse large results easily.

Disclosure: I am pprofile author.

Answer 3

Just to improve @Joe Kington 's above-mentioned answer.

For Python 3.x, use line_profiler:

---

Installation:

pip install line_profiler

Usage:

Suppose you have the program main.py and within it, functions fun_a() and fun_b() that you want to profile with respect to time; you will need to use the decorator @profile just before the function definitions. For e.g.,

@profile
def fun_a():
    #do something

@profile
def fun_b():
    #do something more

if __name__ == '__main__':
    fun_a()
    fun_b()

The program can be profiled by executing the shell command:

$ kernprof -l -v main.py

The arguments can be fetched using $ kernprof -h

Usage: kernprof [-s setupfile] [-o output_file_path] scriptfile [arg] ...

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -l, --line-by-line    Use the line-by-line profiler from the line_profiler
                        module instead of Profile. Implies --builtin.
  -b, --builtin         Put 'profile' in the builtins. Use 'profile.enable()'
                        and 'profile.disable()' in your code to turn it on and
                        off, or '@profile' to decorate a single function, or
                        'with profile:' to profile a single section of code.
  -o OUTFILE, --outfile=OUTFILE
                        Save stats to <outfile>
  -s SETUP, --setup=SETUP
                        Code to execute before the code to profile
  -v, --view            View the results of the profile in addition to saving
                        it.

The results will be printed on the console as:

Total time: 17.6699 s
File: main.py
Function: fun_a at line 5

Line #      Hits         Time  Per Hit   % Time  Line Contents
==============================================================
    5                                           @profile
    6                                           def fun_a():
...

---

EDIT: The results from the profilers can be parsed using the TAMPPA package. Using it, we can get line-by-line desired plots as

Answer 4

You can take help of line_profiler package for this

1. 1st install the package:

    pip install line_profiler

2. Use magic command to load the package to your python/notebook environment

    %load_ext line_profiler

3. If you want to profile the codes for a function then
do as follows:

    %lprun -f demo_func demo_func(arg1, arg2)

you will get a nice formatted output with all the details if you follow these steps :)

Line #      Hits      Time    Per Hit   % Time  Line Contents
 1                                           def demo_func(a,b):
 2         1        248.0    248.0     64.8      print(a+b)
 3         1         40.0     40.0     10.4      print(a)
 4         1         94.0     94.0     24.5      print(a*b)
 5         1          1.0      1.0      0.3      return a/b

Answer 5

PyVmMonitor has a live-view which can help you there (you can connect to a running program and get statistics from it).

See: http://www.pyvmmonitor.com/