templates: add filter to reverse list
The filter supports only lists because for lists, it’s straightforward to
implement. Reversing text doesn’t seem very useful and is hard to implement.
Reversing the bytes would break multi-bytes encodings. Reversing the code
points would break characters consisting of multiple code points. Reversing
graphemes is non-trivial without using a library not included in the standard
library.
# memorytop requires Python 3.4
#
# Usage: set PYTHONTRACEMALLOC=n in the environment of the hg invocation,
# where n>= is the number of frames to show in the backtrace. Put calls to
# memorytop in strategic places to show the current memory use by allocation
# site.
import gc
import tracemalloc
def memorytop(limit=10):
gc.collect()
snapshot = tracemalloc.take_snapshot()
snapshot = snapshot.filter_traces(
(
tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
tracemalloc.Filter(False, "<frozen importlib._bootstrap_external>"),
tracemalloc.Filter(False, "<unknown>"),
)
)
stats = snapshot.statistics('traceback')
total = sum(stat.size for stat in stats)
print("\nTotal allocated size: %.1f KiB\n" % (total / 1024))
print("Lines with the biggest net allocations")
for index, stat in enumerate(stats[:limit], 1):
print(
"#%d: %d objects using %.1f KiB"
% (index, stat.count, stat.size / 1024)
)
for line in stat.traceback.format(most_recent_first=True):
print(' ', line)
other = stats[limit:]
if other:
size = sum(stat.size for stat in other)
count = sum(stat.count for stat in other)
print(
"%s other: %d objects using %.1f KiB"
% (len(other), count, size / 1024)
)
print()