( )⚙ D1337 util: add util.clearcachedproperty

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Differential D1337

util: add util.clearcachedproperty
ClosedPublic

Authored by mbthomas on Nov 8 2017, 12:30 PM.

Details

Reviewers
indygreg
durin42
Group Reviewers
hg-reviewers
Commits
rHGbe6aa0cff8ea: util: add util.clearcachedproperty
Summary

This utility function allows clearing of the cached value set up
@propertycache, if there is one.

Diff Detail

Repository
rHG Mercurial
Lint
Lint Skipped
Unit
Unit Tests Skipped

Event Timeline

mbthomas created this revision.Nov 8 2017, 12:30 PM
indygreg accepted this revision.Nov 10 2017, 12:18 AM
indygreg added a subscriber: indygreg.
indygreg added inline comments.
mercurial/util.py
936–937

This pattern is commonly implemented using a `try..except KeyError around the del`. This avoids the double key lookup and I /think/ is faster.

But since this is a super small function and won't be called with high frequency (I assume), it shouldn't be a problem. If a loop were so tight that it mattered, execution time would be dominated by Python function call overhead, not the low-level primitives inside the function.

This revision is now accepted and ready to land.Nov 10 2017, 12:18 AM
durin42 accepted this revision.Nov 10 2017, 5:12 PM
Closed by commit rHGbe6aa0cff8ea: util: add util.clearcachedproperty (authored by mbthomas). · Explain WhyNov 10 2017, 6:03 PM
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Mmercurial/util.py (5 lines)

Diff 3337

mercurial/util.py

result = self.func(obj) result = self.func(obj)
self.cachevalue(obj, result) self.cachevalue(obj, result)
return result return result
def cachevalue(self, obj, value): def cachevalue(self, obj, value):
# __dict__ assignment required to bypass __setattr__ (eg: repoview) # __dict__ assignment required to bypass __setattr__ (eg: repoview)
obj.__dict__[self.name] = value obj.__dict__[self.name] = value
def clearcachedproperty(obj, prop):
'''clear a cached property value, if one has been set'''
if prop in obj.__dict__:
del obj.__dict__[prop]
indygregUnsubmitted
Not Done

This pattern is commonly implemented using a `try..except KeyError around the del`. This avoids the double key lookup and I /think/ is faster.

But since this is a super small function and won't be called with high frequency (I assume), it shouldn't be a problem. If a loop were so tight that it mattered, execution time would be dominated by Python function call overhead, not the low-level primitives inside the function.

indygreg: This pattern is commonly implemented using a ``try..except KeyError`` around the ``del``. This…
def pipefilter(s, cmd): def pipefilter(s, cmd):
'''filter string S through command CMD, returning its output''' '''filter string S through command CMD, returning its output'''
p = subprocess.Popen(cmd, shell=True, close_fds=closefds, p = subprocess.Popen(cmd, shell=True, close_fds=closefds,
stdin=subprocess.PIPE, stdout=subprocess.PIPE) stdin=subprocess.PIPE, stdout=subprocess.PIPE)
pout, perr = p.communicate(s) pout, perr = p.communicate(s)
return pout return pout
def tempfilter(s, cmd): def tempfilter(s, cmd):