Excluding code from coverage.py
You may have code in your project that you know won’t be executed, and you want to tell coverage.py to ignore it. For example, you may have debugging-only code that won’t be executed during your unit tests. You can tell coverage.py to exclude this code during reporting so that it doesn’t clutter your reports with noise about code that you don’t need to hear about.
Coverage.py will look for comments marking clauses for exclusion. In this code, the “if debug” clause is excluded from reporting:
a = my_function1()
if debug: # pragma: no cover
msg = "blah blah"
log_message(msg, a)
b = my_function2()
By default, any line with a comment of pragma: no cover is excluded. If
that line introduces a clause, for example, an if clause, or a function or
class definition, then the entire clause is also excluded. Here the
__repr__ function is not reported as missing:
class MyObject(object):
def __init__(self):
blah1()
blah2()
def __repr__(self): # pragma: no cover
return "<MyObject>"
Excluded code is executed as usual, and its execution is recorded in the coverage data as usual. When producing reports though, coverage.py excludes it from the list of missing code.
Branch coverage
When measuring branch coverage, a conditional will not be counted as a branch if one of its choices is excluded:
def only_one_choice(x):
if x:
blah1()
blah2()
else: # pragma: no cover
# x is always true.
blah3()
Because the else clause is excluded, the if only has one possible next
line, so it isn’t considered a branch at all.
Default exclusions
Coverage.py has a set of built-in exclusion patterns. For line coverage, these lines are automatically excluded:
Any line with a comment like
# pragma: no cover. Other slight differences in spacing and letter case are also recognized.Any line with only
...in the code, for excluding placeholder function bodies.
For branch coverage, these kinds of branches are automatically excluded:
A branch with a comment like
# pragma: no branch, including differences in spacing and letter case.Some branches that are known at compile time:
if True:,while True:, and so on.A branch just for type checkers:
if TYPE_CHECKING:.
Added in version 7.10.0: the ... and TYPE_CHECKING defaults.
Advanced exclusion
Coverage.py identifies exclusions by matching source code against a list of regular expressions. Using configuration files or the coverage API, you can add to that list. This is useful if you have often-used constructs to exclude that can be matched with a regex. You can exclude them all at once in your configuration without littering your code with exclusion pragmas.
Before coverage.py 7.6.0, the regexes were matched against single lines of your source code. Now they can be multi-line regexes that find matches across lines. See Multi-line exclusion regexes.
If a matched line introduces a block, the entire block is excluded from
reporting. Matching a def line or decorator line will exclude an entire
function.
For example, you might decide that __repr__ functions are usually only used in debugging code, and are uninteresting to test themselves. You could exclude all of them by adding a regex to the exclusion list:
[tool.coverage.report]
exclude_also = [
"def __repr__",
]
[report]
exclude_also =
def __repr__
# You can also use sections like [tool.coverage.run]
[report]
exclude_also = [
"def __repr__",
]
[coverage:report]
exclude_also =
def __repr__
For example, here’s a list of exclusions I’ve used:
[tool.coverage.report]
exclude_also = [
'def __repr__',
'if self.debug:',
'if settings.DEBUG',
'raise AssertionError',
'raise NotImplementedError',
'if 0:',
'if __name__ == .__main__.:',
'if TYPE_CHECKING:',
'class .*\bProtocol\):',
'@(abc\.)?abstractmethod',
]
[report]
exclude_also =
def __repr__
if self.debug:
if settings.DEBUG
raise AssertionError
raise NotImplementedError
if 0:
if __name__ == .__main__.:
if TYPE_CHECKING:
class .*\bProtocol\):
@(abc\.)?abstractmethod
# You can also use sections like [tool.coverage.run]
[report]
exclude_also = [
'def __repr__',
'if self.debug:',
'if settings.DEBUG',
'raise AssertionError',
'raise NotImplementedError',
'if 0:',
'if __name__ == .__main__.:',
'if TYPE_CHECKING:',
'class .*\bProtocol\):',
'@(abc\.)?abstractmethod',
]
[coverage:report]
exclude_also =
def __repr__
if self.debug:
if settings.DEBUG
raise AssertionError
raise NotImplementedError
if 0:
if __name__ == .__main__.:
if TYPE_CHECKING:
class .*\bProtocol\):
@(abc\.)?abstractmethod
The [report] exclude_also option adds regexes to the built-in default list so that you can add your own exclusions. The older [report] exclude_lines option completely overwrites the list of regexes.
The regexes only have to match part of a line. Be careful not to over-match.
The regex ... will match any line with more than three characters in it,
which is certainly not what you want to exclude.
Multi-line exclusion regexes
Added in version 7.6.0.
Exclusion regexes can match multi-line regions. All of the lines in a matched region will be excluded. If part of the region introduces a block, the entire block is excluded even if part of it is outside the matched region.
When writing regexes to match multiple lines, remember that "." won’t match
a newline character, but "\n" or "(?s:.)" will. The regexes in these
settings are combined, so you cannot use global flags like (?s) in
your regexes. Use the scoped flag form instead: (?s:...)
Here are some examples:
[tool.coverage.report]
exclude_also = [
# 1. Exclude an except clause of a specific form:
'except ValueError:\n\s*assume\(False\)',
# 2. Comments to turn coverage on and off:
'no cover: start(?s:.)*?no cover: stop',
# 3. A pragma comment that excludes an entire file:
'\A(?s:.*# pragma: exclude file.*)\Z',
]
[report]
exclude_also =
; 1. Exclude an except clause of a specific form:
except ValueError:\n\s*assume\(False\)
; 2. Comments to turn coverage on and off:
no cover: start(?s:.)*?no cover: stop
; 3. A pragma comment that excludes an entire file:
\A(?s:.*# pragma: exclude file.*)\Z
# You can also use sections like [tool.coverage.run]
[report]
exclude_also = [
# 1. Exclude an except clause of a specific form:
'except ValueError:\n\s*assume\(False\)',
# 2. Comments to turn coverage on and off:
'no cover: start(?s:.)*?no cover: stop',
# 3. A pragma comment that excludes an entire file:
'\A(?s:.*# pragma: exclude file.*)\Z',
]
[coverage:report]
exclude_also =
; 1. Exclude an except clause of a specific form:
except ValueError:\n\s*assume\(False\)
; 2. Comments to turn coverage on and off:
no cover: start(?s:.)*?no cover: stop
; 3. A pragma comment that excludes an entire file:
\A(?s:.*# pragma: exclude file.*)\Z
The first regex matches a specific except line followed by a specific function
call. Both lines must be present for the exclusion to take effect. Note that
the regex uses "\n\s*" to match the newline and the indentation of the
second line. Without these, the regex won’t match.
The second regex creates a pair of comments that can be used to exclude
statements between them. All lines between # no cover: start and # no
cover: stop will be excluded. The regex doesn’t start with # because
that’s a comment in a .coveragerc file. Be careful with wildcards: we’ve used
the non-greedy *? to match the fewest possible characters between the
comments. If you used the greedy * instead, the star would match as many
as possible, and you could accidentally exclude large swaths of code.
The third regex matches the entire text of a file containing the comment #
pragma: exclude file. This lets you exclude files from coverage measurement
with an internal comment instead of naming them in a settings file. This regex
uses the "(?s:...)" regex flag to let a dot match any character including a
newline.
Excluding source files
See Specifying source files for ways to limit what files coverage.py measures or reports on.