我最近对算法感兴趣,并开始通过编写一个简单的实现,然后以各种方式优化它来探索它们.
我已经熟悉用于分析运行时的标准Python模块(对于大多数事情我已经发现IPython中的timeit魔术功能已足够),但我也对内存使用感兴趣,所以我也可以探索这些权衡(例如,缓存先前计算的值表的成本与根据需要重新计算它们的成本.是否有一个模块可以为我分析给定函数的内存使用情况？
这个已经在这里得到了解答:Python内存分析器
基本上你做了类似的事情(引自Guppy-PE):
>>> from guppy import hpy; h=hpy()
>>> h.heap()
Partition of a set of 48477 objects. Total size = 3265516 bytes.
Index Count % Size % Cumulative % Kind (class / dict of class)
0 25773 53 1612820 49 1612820 49 str
1 11699 24 483960 15 2096780 64 tuple
2 174 0 241584 7 2338364 72 dict of module
3 3478 7 222592 7 2560956 78 types.CodeType
4 3296 7 184576 6 2745532 84 function
5 401 1 175112 5 2920644 89 dict of class
6 108 0 81888 3 3002532 92 dict (no owner)
7 114 0 79632 2 3082164 94 dict of type
8 117 0 51336 2 3133500 96 type
9 667 1 24012 1 3157512 97 __builtin__.wrapper_descriptor
<76 more rows. Type e.g. '_.more' to view.>
>>> h.iso(1,[],{})
Partition of a set of 3 objects. Total size = 176 bytes.
Index Count % Size % Cumulative % Kind (class / dict of class)
0 1 33 136 77 136 77 dict (no owner)
1 1 33 28 16 164 93 list
2 1 33 12 7 176 100 int
>>> x=[]
>>> h.iso(x).sp
0: h.Root.i0_modules['__main__'].__dict__['x']
>>>
Python 3.4包含一个新模块:tracemalloc.它提供有关哪些代码分配最多内存的详细统计信息.这是一个显示分配内存的前三行的示例.
from collections import Counter
import linecache
import os
import tracemalloc
def display_top(snapshot, key_type='lineno', limit=3):
snapshot = snapshot.filter_traces((
tracemalloc.Filter(False, ""),
tracemalloc.Filter(False, ""),
))
top_stats = snapshot.statistics(key_type)
print("Top %s lines" % limit)
for index, stat in enumerate(top_stats[:limit], 1):
frame = stat.traceback[0]
# replace "/path/to/module/file.py" with "module/file.py"
filename = os.sep.join(frame.filename.split(os.sep)[-2:])
print("#%s: %s:%s: %.1f KiB"
% (index, filename, frame.lineno, stat.size / 1024))
line = linecache.getline(frame.filename, frame.lineno).strip()
if line:
print(' %s' % line)
other = top_stats[limit:]
if other:
size = sum(stat.size for stat in other)
print("%s other: %.1f KiB" % (len(other), size / 1024))
total = sum(stat.size for stat in top_stats)
print("Total allocated size: %.1f KiB" % (total / 1024))
tracemalloc.start()
counts = Counter()
fname = '/usr/share/dict/american-english'
with open(fname) as words:
words = list(words)
for word in words:
prefix = word[:3]
counts[prefix] += 1
print('Top prefixes:', counts.most_common(3))
snapshot = tracemalloc.take_snapshot()
display_top(snapshot)
以下是结果:
Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
Top 3 lines
#1: scratches/memory_test.py:37: 6527.1 KiB
words = list(words)
#2: scratches/memory_test.py:39: 247.7 KiB
prefix = word[:3]
#3: scratches/memory_test.py:40: 193.0 KiB
counts[prefix] += 1
4 other: 4.3 KiB
Total allocated size: 6972.1 KiB
当计算结束时仍然保留内存时,这个例子很棒,但有时你会有分配大量内存的代码,然后释放所有内存.它在技术上不是内存泄漏,但它使用的内存比你想象的要多.如何释放内存时如何跟踪内存使用情况？如果它是您的代码,您可以添加一些调试代码以在其运行时拍摄快照.如果没有,您可以启动后台线程来监视主线程运行时的内存使用情况.
这是前面的示例,其中代码已全部移入count_prefixes()函数中.当该函数返回时,释放所有内存.我还添加了一些sleep()调用来模拟长时间运行的计算.
from collections import Counter
import linecache
import os
import tracemalloc
from time import sleep
def count_prefixes():
sleep(2) # Start up time.
counts = Counter()
fname = '/usr/share/dict/american-english'
with open(fname) as words:
words = list(words)
for word in words:
prefix = word[:3]
counts[prefix] += 1
sleep(0.0001)
most_common = counts.most_common(3)
sleep(3) # Shut down time.
return most_common
def main():
tracemalloc.start()
most_common = count_prefixes()
print('Top prefixes:', most_common)
snapshot = tracemalloc.take_snapshot()
display_top(snapshot)
def display_top(snapshot, key_type='lineno', limit=3):
snapshot = snapshot.filter_traces((
tracemalloc.Filter(False, ""),
tracemalloc.Filter(False, ""),
))
top_stats = snapshot.statistics(key_type)
print("Top %s lines" % limit)
for index, stat in enumerate(top_stats[:limit], 1):
frame = stat.traceback[0]
# replace "/path/to/module/file.py" with "module/file.py"
filename = os.sep.join(frame.filename.split(os.sep)[-2:])
print("#%s: %s:%s: %.1f KiB"
% (index, filename, frame.lineno, stat.size / 1024))
line = linecache.getline(frame.filename, frame.lineno).strip()
if line:
print(' %s' % line)
other = top_stats[limit:]
if other:
size = sum(stat.size for stat in other)
print("%s other: %.1f KiB" % (len(other), size / 1024))
total = sum(stat.size for stat in top_stats)
print("Total allocated size: %.1f KiB" % (total / 1024))
main()
当我运行该版本时,内存使用量从6MB减少到4KB,因为该函数在完成后释放了所有内存.
Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
Top 3 lines
#1: collections/__init__.py:537: 0.7 KiB
self.update(*args, **kwds)
#2: collections/__init__.py:555: 0.6 KiB
return _heapq.nlargest(n, self.items(), key=_itemgetter(1))
#3: python3.6/heapq.py:569: 0.5 KiB
result = [(key(elem), i, elem) for i, elem in zip(range(0, -n, -1), it)]
10 other: 2.2 KiB
Total allocated size: 4.0 KiB
现在,这是一个受另一个答案启发的版本,它启动了第二个线程来监控内存使用情况.
from collections import Counter
import linecache
import os
import tracemalloc
from datetime import datetime
from queue import Queue, Empty
from resource import getrusage, RUSAGE_SELF
from threading import Thread
from time import sleep
def memory_monitor(command_queue: Queue, poll_interval=1):
tracemalloc.start()
old_max = 0
snapshot = None
while True:
try:
command_queue.get(timeout=poll_interval)
if snapshot is not None:
print(datetime.now())
display_top(snapshot)
return
except Empty:
max_rss = getrusage(RUSAGE_SELF).ru_maxrss
if max_rss > old_max:
old_max = max_rss
snapshot = tracemalloc.take_snapshot()
print(datetime.now(), 'max RSS', max_rss)
def count_prefixes():
sleep(2) # Start up time.
counts = Counter()
fname = '/usr/share/dict/american-english'
with open(fname) as words:
words = list(words)
for word in words:
prefix = word[:3]
counts[prefix] += 1
sleep(0.0001)
most_common = counts.most_common(3)
sleep(3) # Shut down time.
return most_common
def main():
queue = Queue()
poll_interval = 0.1
monitor_thread = Thread(target=memory_monitor, args=(queue, poll_interval))
monitor_thread.start()
try:
most_common = count_prefixes()
print('Top prefixes:', most_common)
finally:
queue.put('stop')
monitor_thread.join()
def display_top(snapshot, key_type='lineno', limit=3):
snapshot = snapshot.filter_traces((
tracemalloc.Filter(False, ""),
tracemalloc.Filter(False, ""),
))
top_stats = snapshot.statistics(key_type)
print("Top %s lines" % limit)
for index, stat in enumerate(top_stats[:limit], 1):
frame = stat.traceback[0]
# replace "/path/to/module/file.py" with "module/file.py"
filename = os.sep.join(frame.filename.split(os.sep)[-2:])
print("#%s: %s:%s: %.1f KiB"
% (index, filename, frame.lineno, stat.size / 1024))
line = linecache.getline(frame.filename, frame.lineno).strip()
if line:
print(' %s' % line)
other = top_stats[limit:]
if other:
size = sum(stat.size for stat in other)
print("%s other: %.1f KiB" % (len(other), size / 1024))
total = sum(stat.size for stat in top_stats)
print("Total allocated size: %.1f KiB" % (total / 1024))
main()
该resource模块允许您检查当前内存使用情况,并从峰值内存使用情况中保存快照.队列允许主线程告诉内存监视器线程何时打印其报告并关闭.运行时,它显示list()调用使用的内存:
2018-05-29 10:34:34.441334 max RSS 10188
2018-05-29 10:34:36.475707 max RSS 23588
2018-05-29 10:34:36.616524 max RSS 38104
2018-05-29 10:34:36.772978 max RSS 45924
2018-05-29 10:34:36.929688 max RSS 46824
2018-05-29 10:34:37.087554 max RSS 46852
Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
2018-05-29 10:34:56.281262
Top 3 lines
#1: scratches/scratch.py:36: 6527.0 KiB
words = list(words)
#2: scratches/scratch.py:38: 16.4 KiB
prefix = word[:3]
#3: scratches/scratch.py:39: 10.1 KiB
counts[prefix] += 1
19 other: 10.8 KiB
Total allocated size: 6564.3 KiB
如果你在Linux上,你会发现/proc/self/statm比resource模块更有用.
如果你只想查看一个对象的内存使用情况,(回答其他问题)
有一个名为Pympler的
asizeof模块,它包含模块.使用方法如下:
from pympler import asizeof asizeof.asizeof(my_object)
sys.getsizeof与之不同,它适用于您自己创建的对象.>>> asizeof.asizeof(tuple('bcd')) 200 >>> asizeof.asizeof({'foo': 'bar', 'baz': 'bar'}) 400 >>> asizeof.asizeof({}) 280 >>> asizeof.asizeof({'foo':'bar'}) 360 >>> asizeof.asizeof('foo') 40 >>> asizeof.asizeof(Bar()) 352 >>> asizeof.asizeof(Bar().__dict__) 280
>>> help(asizeof.asizeof)
Help on function asizeof in module pympler.asizeof:
asizeof(*objs, **opts)
Return the combined size in bytes of all objects passed as positional arguments.
对于一个非常简单的方法尝试:
import resource
def using(point=""):
usage=resource.getrusage(resource.RUSAGE_SELF)
return '''%s: usertime=%s systime=%s mem=%s mb
'''%(point,usage[0],usage[1],
(usage[2]*resource.getpagesize())/1000000.0 )
只需插入using("Label")您想要查看正在发生的事情的位置即可.
我认为既然已接受的答案以及投票数第二高的答案都存在一些问题，所以我想再提供一个基于Ihor B.答案的答案，并进行了一些小而重要的修改。
该解决方案允许您运行分析上或者通过包装函数调用用profile，功能和调用它或通过与装饰你的函数/法@profile装饰。
当您要分析一些第三方代码而不弄乱其源代码时，第一种技术很有用，而第二种技术则比较“干净”，当您不介意修改函数/方法的源代码时，效果更好想要简介。
我还修改了输出，以便获得RSS，VMS和共享内存。我不太关心“之前”和“之后”的值，只关心增量，因此我删除了这些值（如果您要与Ihor B.的答案进行比较）。
分析代码# profile.py
import time
import os
import psutil
import inspect
def elapsed_since(start):
#return time.strftime("%H:%M:%S", time.gmtime(time.time() - start))
elapsed = time.time() - start
if elapsed < 1:
return str(round(elapsed*1000,2)) + "ms"
if elapsed < 60:
return str(round(elapsed, 2)) + "s"
if elapsed < 3600:
return str(round(elapsed/60, 2)) + "min"
else:
return str(round(elapsed / 3600, 2)) + "hrs"
def get_process_memory():
process = psutil.Process(os.getpid())
mi = process.memory_info()
return mi.rss, mi.vms, mi.shared
def format_bytes(bytes):
if abs(bytes) < 1000:
return str(bytes)+"B"
elif abs(bytes) < 1e6:
return str(round(bytes/1e3,2)) + "kB"
elif abs(bytes) < 1e9:
return str(round(bytes / 1e6, 2)) + "MB"
else:
return str(round(bytes / 1e9, 2)) + "GB"
def profile(func, *args, **kwargs):
def wrapper(*args, **kwargs):
rss_before, vms_before, shared_before = get_process_memory()
start = time.time()
result = func(*args, **kwargs)
elapsed_time = elapsed_since(start)
rss_after, vms_after, shared_after = get_process_memory()
print("Profiling: {:>20} RSS: {:>8} | VMS: {:>8} | SHR {"
":>8} | time: {:>8}"
.format("<" + func.__name__ + ">",
format_bytes(rss_after - rss_before),
format_bytes(vms_after - vms_before),
format_bytes(shared_after - shared_before),
elapsed_time))
return result
if inspect.isfunction(func):
return wrapper
elif inspect.ismethod(func):
return wrapper(*args,**kwargs)
用法示例，假设上面的代码另存为profile.py：
from profile import profile
from time import sleep
from sklearn import datasets # Just an example of 3rd party function call
# Method 1
run_profiling = profile(datasets.load_digits)
data = run_profiling()
# Method 2
@profile
def my_function():
# do some stuff
a_list = []
for i in range(1,100000):
a_list.append(i)
return a_list
res = my_function()
这将导致输出类似于以下内容：
Profiling:RSS: 5.07MB | VMS: 4.91MB | SHR 73.73kB | time: 89.99ms Profiling: RSS: 1.06MB | VMS: 1.35MB | SHR 0B | time: 8.43ms
请记住，这种分析方法仅是近似的，因为计算机上可能会发生很多其他事情。由于垃圾收集和其他因素，增量甚至可能为零。
由于某些未知的原因，出现非常短的函数调用（例如1或2 ms），而内存使用量为零。我怀疑这是硬件/操作系统（在装有Linux的基本笔记本电脑上测试过）在内存统计信息更新频率方面的一些限制。
为了使示例简单，我没有使用任何函数参数，但是它们应该像预期的那样工作，即
profile(my_function, arg)进行概要分析my_function(arg)
下面是一个简单的函数装饰器，它可以跟踪函数调用之前，函数调用之后进程消耗的内存量以及它们之间的区别：
import time
import os
import psutil
def elapsed_since(start):
return time.strftime("%H:%M:%S", time.gmtime(time.time() - start))
def get_process_memory():
process = psutil.Process(os.getpid())
return process.get_memory_info().rss
def profile(func):
def wrapper(*args, **kwargs):
mem_before = get_process_memory()
start = time.time()
result = func(*args, **kwargs)
elapsed_time = elapsed_since(start)
mem_after = get_process_memory()
print("{}: memory before: {:,}, after: {:,}, consumed: {:,}; exec time: {}".format(
func.__name__,
mem_before, mem_after, mem_after - mem_before,
elapsed_time))
return result
return wrapper
这是我的博客，描述了所有详细信息。（已归档的链接）
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