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Add __repr__ method to metric objects, make them debug friendly. #481

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Oct 30, 2019
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Add __repr__ method to metric objects, make them debug friendly. #481

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6eb1a57
Add __repr__ method to metric objects, make them debug friendly.
asherf Oct 26, 2019
e1274a8
Added __str__ too, update repr to use parenthesis to be more pythonic.
asherf Oct 29, 2019
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4 changes: 4 additions & 0 deletions prometheus_client/metrics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,10 @@ def collect(self):
metric.add_sample(self._name + suffix, labels, value)
return [metric]

def __repr__(self):
metric_type = type(self)
return "{0}.{1}:{2}".format(metric_type.__module__, metric_type.__name__, self._name)
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A repr() should in principle allow instantiation of the object. This would be a __str__. Also _type covers you more here.

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@asherf asherf Oct 29, 2019 •
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As far as using the _type, I added an __str__ implementation that uses it.
I think having the full type path is useful in repr output which what is used in debuggers.
I updated the __repr__ implementation to use parenthesis instead of a column to be more compatible with the ability to pass eval
However, I feel that making it a 100% compatible with that (i.e. an eval(repr(metric)) that produces an identical object) will result in a string that will be too noisy and thus less useful when debugging.


def __init__(self,
name,
documentation,
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18 changes: 18 additions & 0 deletions tests/test_core.py
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Expand Up @@ -30,9 +30,13 @@ def test_increment(self):
self.assertEqual(1, self.registry.get_sample_value('c_total'))
self.counter.inc(7)
self.assertEqual(8, self.registry.get_sample_value('c_total'))

def test_repr(self):
self.assertEqual(repr(self.counter), "prometheus_client.metrics.Counter:c")

def test_negative_increment_raises(self):
self.assertRaises(ValueError, self.counter.inc, -1)


def test_function_decorator(self):
@self.counter.count_exceptions(ValueError)
Expand Down Expand Up @@ -83,6 +87,9 @@ class TestGauge(unittest.TestCase):
def setUp(self):
self.registry = CollectorRegistry()
self.gauge = Gauge('g', 'help', registry=self.registry)

def test_repr(self):
self.assertEqual(repr(self.gauge), "prometheus_client.metrics.Gauge:g")

def test_gauge(self):
self.assertEqual(0, self.registry.get_sample_value('g'))
Expand Down Expand Up @@ -180,6 +187,9 @@ def setUp(self):
self.registry = CollectorRegistry()
self.summary = Summary('s', 'help', registry=self.registry)

def test_repr(self):
self.assertEqual(repr(self.summary), "prometheus_client.metrics.Summary:s")

def test_summary(self):
self.assertEqual(0, self.registry.get_sample_value('s_count'))
self.assertEqual(0, self.registry.get_sample_value('s_sum'))
Expand Down Expand Up @@ -269,6 +279,10 @@ def setUp(self):
self.histogram = Histogram('h', 'help', registry=self.registry)
self.labels = Histogram('hl', 'help', ['l'], registry=self.registry)

def test_repr(self):
self.assertEqual(repr(self.histogram), "prometheus_client.metrics.Histogram:h")
self.assertEqual(repr(self.labels), "prometheus_client.metrics.Histogram:hl")

def test_histogram(self):
self.assertEqual(0, self.registry.get_sample_value('h_bucket', {'le': '1.0'}))
self.assertEqual(0, self.registry.get_sample_value('h_bucket', {'le': '2.5'}))
Expand Down Expand Up @@ -373,6 +387,10 @@ def setUp(self):
self.info = Info('i', 'help', registry=self.registry)
self.labels = Info('il', 'help', ['l'], registry=self.registry)

def test_repr(self):
self.assertEqual(repr(self.info), "prometheus_client.metrics.Info:i")
self.assertEqual(repr(self.labels), "prometheus_client.metrics.Info:il")

def test_info(self):
self.assertEqual(1, self.registry.get_sample_value('i_info', {}))
self.info.info({'a': 'b', 'c': 'd'})
Expand Down