mybisect

Use this package to help with ad-hoc bisect operations for the first occurence of something (usually a good or bad build when working with build systems).

If you're looking specifically for a version in a git or mercurial repository, see git bisect and hg bisect for more specialized tools.

Bisecting by invoking as script

To use mybisect as a command, prepare a file with one value per line, and invoke python3 mybisect --command "command {}" FILE.

The command should be a python string to be formatted with the input from the line. If the command is not provided, the line itself is used as a command.

The result is printed out with the format first fail value at INDEX: VALUE, which can be useful to know if you want to grep for it (note that the index is zero-based).

Example (Windows)

Create a test file called testdata.txt:

pass
pass
pass
pass
fail
fail

Create a batch file called test.bat:

@echo off
if "%1" == "fail" (
  echo found failure
  exit /b 1
)
exit /b 0

When you run python3 mybisect.py -c "test.bat {}" testdata.txt, you will see this output:

pass value at 2: pass
found failure
fail value at 4: fail
pass value at 3: pass
first fail value at 4: fail

Bisecting with code

To use mybisect as a library, use the bisect function, passing in a list of values and a callback function to test whether a value fails a test. An optional third value is a callback to write out progress messages.

The function will return a tuple with the first value that fails and its index.

If the function finds no failing value, it will return (None, -1) instead.

Running tests

Run python3 test_mybisect.py