The CoverageData class

New in version 4.0.

class coverage.CoverageData(basename=None, suffix=None, no_disk=False, warn=None, debug=None)

Manages collected coverage data, including file storage.

This class is the public supported API to the data that coverage.py collects during program execution. It includes information about what code was executed. It does not include information from the analysis phase, to determine what lines could have been executed, or what lines were not executed.

Note

The data file is currently a SQLite database file, with a documented schema. The schema is subject to change though, so be careful about querying it directly. Use this API if you can to isolate yourself from changes.

There are a number of kinds of data that can be collected:

  • lines: the line numbers of source lines that were executed. These are always available.

  • arcs: pairs of source and destination line numbers for transitions between source lines. These are only available if branch coverage was used.

  • file tracer names: the module names of the file tracer plugins that handled each file in the data.

Lines, arcs, and file tracer names are stored for each source file. File names in this API are case-sensitive, even on platforms with case-insensitive file systems.

A data file either stores lines, or arcs, but not both.

A data file is associated with the data when the CoverageData is created, using the parameters basename, suffix, and no_disk. The base name can be queried with base_filename(), and the actual file name being used is available from data_filename().

To read an existing coverage.py data file, use read(). You can then access the line, arc, or file tracer data with lines(), arcs(), or file_tracer().

The has_arcs() method indicates whether arc data is available. You can get a set of the files in the data with measured_files(). As with most Python containers, you can determine if there is any data at all by using this object as a boolean value.

The contexts for each line in a file can be read with contexts_by_lineno().

To limit querying to certain contexts, use set_query_context() or set_query_contexts(). These will narrow the focus of subsequent lines(), arcs(), and contexts_by_lineno() calls. The set of all measured context names can be retrieved with measured_contexts().

Most data files will be created by coverage.py itself, but you can use methods here to create data files if you like. The add_lines(), add_arcs(), and add_file_tracers() methods add data, in ways that are convenient for coverage.py.

To record data for contexts, use set_context() to set a context to be used for subsequent add_lines() and add_arcs() calls.

To add a source file without any measured data, use touch_file().

Write the data to its file with write().

You can clear the data in memory with erase(). Two data collections can be combined by using update() on one CoverageData, passing it the other.

Data in a CoverageData can be serialized and deserialized with dumps() and loads().

__init__(basename=None, suffix=None, no_disk=False, warn=None, debug=None)

Create a CoverageData object to hold coverage-measured data.

Parameters
  • basename (str) – the base name of the data file, defaulting to “.coverage”.

  • suffix (str or bool) – has the same meaning as the data_suffix argument to coverage.Coverage.

  • no_disk (bool) – if True, keep all data in memory, and don’t write any disk file.

  • warn – a warning callback function, accepting a warning message argument.

  • debug – a debug callback function.

add_arcs(arc_data)

Add measured arc data.

arc_data is a dictionary mapping file names to dictionaries:

{ filename: { (l1,l2): None, ... }, ...}
add_file_tracers(file_tracers)

Add per-file plugin information.

file_tracers is { filename: plugin_name, … }

add_lines(line_data)

Add measured line data.

line_data is a dictionary mapping file names to dictionaries:

{ filename: { lineno: None, ... }, ...}
arcs(filename)

Get the list of arcs executed for a file.

If the file was not measured, returns None. A file might be measured, and have no arcs executed, in which case an empty list is returned.

If the file was executed, returns a list of 2-tuples of integers. Each pair is a starting line number and an ending line number for a transition from one line to another. The list is in no particular order.

Negative numbers have special meaning. If the starting line number is -N, it represents an entry to the code object that starts at line N. If the ending ling number is -N, it’s an exit from the code object that starts at line N.

base_filename()

The base filename for storing data.

New in version 5.0.

contexts_by_lineno(filename)

Get the contexts for each line in a file.

Returns

A dict mapping line numbers to a list of context names.

New in version 5.0.

data_filename()

Where is the data stored?

New in version 5.0.

dumps()

Serialize the current data to a byte string.

The format of the serialized data is not documented. It is only suitable for use with loads() in the same version of coverage.py.

Returns

A byte string of serialized data.

New in version 5.0.

erase(parallel=False)

Erase the data in this object.

If parallel is true, then also deletes data files created from the basename by parallel-mode.

file_tracer(filename)

Get the plugin name of the file tracer for a file.

Returns the name of the plugin that handles this file. If the file was measured, but didn’t use a plugin, then “” is returned. If the file was not measured, then None is returned.

has_arcs()

Does the database have arcs (True) or lines (False).

lines(filename)

Get the list of lines executed for a file.

If the file was not measured, returns None. A file might be measured, and have no lines executed, in which case an empty list is returned.

If the file was executed, returns a list of integers, the line numbers executed in the file. The list is in no particular order.

loads(data)

Deserialize data from dumps()

Use with a newly-created empty CoverageData object. It’s undefined what happens if the object already has data in it.

Parameters

data – A byte string of serialized data produced by dumps().

New in version 5.0.

measured_contexts()

A set of all contexts that have been measured.

New in version 5.0.

measured_files()

A set of all files that had been measured.

read()

Start using an existing data file.

set_context(context)

Set the current context for future add_lines() etc.

context is a str, the name of the context to use for the next data additions. The context persists until the next set_context().

New in version 5.0.

set_query_context(context)

Set a context for subsequent querying.

The next lines(), arcs(), or contexts_by_lineno() calls will be limited to only one context. context is a string which must match a context exactly. If it does not, no exception is raised, but queries will return no data.

New in version 5.0.

set_query_contexts(contexts)

Set a number of contexts for subsequent querying.

The next lines(), arcs(), or contexts_by_lineno() calls will be limited to the specified contexts. contexts is a list of Python regular expressions. Contexts will be matched using re.search. Data will be included in query results if they are part of any of the contexts matched.

New in version 5.0.

classmethod sys_info()

Our information for Coverage.sys_info.

Returns a list of (key, value) pairs.

touch_file(filename, plugin_name='')

Ensure that filename appears in the data, empty if needed.

plugin_name is the name of the plugin responsible for this file. It is used to associate the right filereporter, etc.

update(other_data, aliases=None)

Update this data with data from several other CoverageData instances.

If aliases is provided, it’s a PathAliases object that is used to re-map paths to match the local machine’s.

write()

Ensure the data is written to the data file.