Created 24 May 2009, last updated 21 February 2010

The API to coverage.py is very simple, contained in a single module called coverage. Most of the interface is in a single class, also called coverage. Methods on the coverage object correspond to operations available in the command line interface. For example, a simple use would be:

import coverage cov = coverage.coverage() cov.start() # .. run your code .. cov.stop() cov.save()

The coverage module

class coverage.coverage(data_file=None, data_suffix=None, cover_pylib=None, auto_data=False, timid=None, branch=None, config_file=True)

Programmatic access to Coverage.

To use:

from coverage import coverage cov = coverage() cov.start() #.. blah blah (run your code) blah blah .. cov.stop() cov.html_report(directory='covhtml')

data_file is the base name of the data file to use, defaulting to “.coverage”. data_suffix is appended (with a dot) to data_file to create the final file name. If data_suffix is simply True, then a suffix is created with the machine and process identity included.

cover_pylib is a boolean determining whether Python code installed with the Python interpreter is measured. This includes the Python standard library and any packages installed with the interpreter.

If auto_data is true, then any existing data file will be read when coverage measurement starts, and data will be saved automatically when measurement stops.

If timid is true, then a slower and simpler trace function will be used. This is important for some environments where manipulation of tracing functions breaks the faster trace function.

If branch is true, then branch coverage will be measured in addition to the usual statement coverage.

config_file determines what config file to read. If it is a string, it is the name of the config file to read. If it is True, then a standard file is read (“.coveragerc”). If it is False, then no file is read.

analysis(morf): Like analysis2 but doesn’t return excluded line numbers.

analysis2(morf)

Analyze a module.

morf is a module or a filename. It will be analyzed to determine its coverage statistics. The return value is a 5-tuple:

The filename for the module.
A list of line numbers of executable statements.
A list of line numbers of excluded statements.
A list of line numbers of statements not run (missing from execution).
A readable formatted string of the missing line numbers.

The analysis uses the source file itself and the current measured coverage data.

annotate(morfs=None, directory=None, ignore_errors=None, omit_prefixes=None)

Annotate a list of modules.

Each module in morfs is annotated. The source is written to a new file, named with a “,cover” suffix, with each line prefixed with a marker to indicate the coverage of the line. Covered lines have “>”, excluded lines have “-“, and missing lines have “!”.

clear_exclude(): Clear the exclude list.

combine()

Combine together a number of similarly-named coverage data files.

All coverage data files whose name starts with data_file (from the coverage() constructor) will be read, and combined together into the current measurements.

erase()

Erase previously-collected coverage data.

This removes the in-memory data collected in this session as well as discarding the data file.

exclude(regex)

Exclude source lines from execution consideration.

regex is a regular expression. Lines matching this expression are not considered executable when reporting code coverage. A list of regexes is maintained; this function adds a new regex to the list. Matching any of the regexes excludes a source line.

get_exclude_list(): Return the list of excluded regex patterns.

html_report(morfs=None, directory=None, ignore_errors=None, omit_prefixes=None): Generate an HTML report.

load(): Load previously-collected coverage data from the data file.

report(morfs=None, show_missing=True, ignore_errors=None, file=None, omit_prefixes=None)

Write a summary report to file.

Each module in morfs is listed, with counts of statements, executed statements, missing statements, and a list of lines missed.

save(): Save the collected coverage data to the data file.

start(): Start measuring code coverage.

stop(): Stop measuring code coverage.

sysinfo(): Return a list of (key, value) pairs showing internal information.

use_cache(usecache)

Control the use of a data file (incorrectly called a cache).

usecache is true or false, whether to read and write data on disk.

xml_report(morfs=None, outfile=None, ignore_errors=None, omit_prefixes=None)

Generate an XML report of coverage results.

The report is compatible with Cobertura reports.

Each module in morfs is included in the report. outfile is the path to write the file to, “-” will write to stdout.

Starting coverage automatically

This function is used to start coverage measurement automatically when Python starts. See Measuring subprocesses for details.

coverage.process_startup()

Call this at Python startup to perhaps measure coverage.

If the environment variable COVERAGE_PROCESS_START is defined, coverage measurement is started. The value of the variable is the config file to use.

There are two ways to configure your Python installation to invoke this function when Python starts:

Create or append to sitecustomize.py to add these lines:
import coverage coverage.process_startup()
Create a .pth file in your Python installation containing:
import coverage; coverage.process_startup()

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