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# Speedup Import
## Assumptions
I created a simple script to run a command 20 times and calculate
the average clock time for each run of the command. This script requires
some unix tools, including the gnu flavor of the `time` command. This script
can is called `mtime.sh` and is included in this branch.
These tests were all run on my 2015 MacBook Pro with a 3.1 GHz Intel Core i7
and 16GB of memory.
## Baseline measurement
First let's see how long it takes to start up python. The longish path here
ensures we aren't measuring the time it takes the pyenv shims to run:
```
$./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c ""
100 iterations
average: real 0.028 user 0.020 sys 0.000
```
## Initial measurement
From commit fbbfe256, which has `__init.py__` importing `cmd2.cmd2.Cmd`
and a bunch of other stuff, we get:
```
$ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.140 user 0.100 sys 0.030
```
From the baseline and this initial measurement, we infer it takes ~110 ms
to import the `cmd2` module.
## Defer unittest
In commit 8bc2c37a we defer the import of `unittest` until we need it to
test a transcript.
```
$./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.131 user 0.091 sys 0.030
```
## Defer InteractiveConsole from code
In commit 6e49661f we defer the import of `InteractiveConsole` until the user
wants to run the `py` command.
```
$ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.131 user 0.090 sys 0.030
```
## Defer atexit, codes, signal, tempfile, copy
In commit a479fa94 we defer 5 imports: atexit, codecs, signal, tempfile, and copy.
```
$ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"100 iterations
average: real 0.120 user 0.081 sys 0.021
```
## Defer datetime, functools, io, subprocess, traceback
In commit d9ca07a9 we defer 5 more imports: datetime, functools, io, subprocess, traceback.
```
$ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.115 user 0.080 sys 0.020
```
## extract AddSubmenu to its own file
In commit ccfdf0f9 we extract AddSubmenu() to it's own file, so it is not
imported or processed by default.
```
$ ./mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.117 user 0.081 sys 0.021
```
## Progress Update
Python takes ~30ms to start up and do nothing. When we began we estimated it took
~110ms to import cmd2. We are now down to about ~90ms, which is approximately a
20% improvement.
## Move more functions into utils
Commit fc495a42 moves a few functions from `cmd2.py` into `utils.py`.
```
$ ~/bin/mtime.sh ~/.pyenv/versions/cmd2-3.6/bin/python -c "import cmd2"
100 iterations
average: real 0.119 user 0.081 sys 0.021
|
