如何在Python中使用零初始化整数array.array对象 [英] How to initialise an integer array.array object with zeros in Python

问题描述

标题相似的问题与Python列表或NumPy有关.这与标准Python库的array.array类有关，请参阅 https://docs .python.org/2/library/array.html

Questions with similar titles are about Python lists or NumPy. This is about the array.array class part of the standard Python library, see https://docs.python.org/2/library/array.html

我想出的快速方法(对于整数类型)是将array.fromfile与/dev/zero一起使用.这是

The fasted approach I came up with (for integer types) is to use array.fromfile with /dev/zero. This is

• 比array.array('L'，[0] * size)快27倍，后者暂时需要比最终数组大两倍的内存，
• 比arrar.array('L'，[0])* size快4.7倍
• 并且比使用自定义可迭代对象快200倍(避免创建大型临时列表).

但是，/dev/zero在某些平台上可能不可用.没有NumPy，非标准模块或我自己的c扩展，还有更好的方法吗?

However, /dev/zero may be unavailable on some platforms. Is there a better way to do this without NumPy, non-standard modules or my own c-extension?

演示程序代码:

import array
import sys
import time

size = 100 * 1000**2
test = sys.argv[1]

class ZeroIterable:
    def __init__(self, size):
        self.size = size
        self.next_index = 0
    def next(self):
        if self.next_index == self.size:
            raise StopIteration
        self.next_index = self.next_index + 1
        return 0
    def __iter__(self):
        return self

t = time.time()
if test == 'Z':
    myarray = array.array('L')
    f = open('/dev/zero', 'rb')
    myarray.fromfile(f, size)
    f.close()
elif test == 'L':
    myarray = array.array('L', [0] * size)
elif test == 'S':
    myarray = array.array('L', [0]) * size
elif test == 'I':
    myarray = array.array('L', ZeroIterable(size))     
print time.time() - t

推荐答案

已更新至Python 3并添加了'B'方法:

Updated to Python 3 and added the 'B' method:

import array
import sys
import time

size = 100 * 1000**2
test = sys.argv[1]

class ZeroIterable:
    def __init__(self, size):
        self.size = size
        self.next_index = 0
    def __next__(self):
        if self.next_index == self.size:
            raise StopIteration
        self.next_index = self.next_index + 1
        return 0
    def __iter__(self):
        return self

t = time.time()
if test == 'Z':
    myarray = array.array('L')
    f = open('/dev/zero', 'rb')
    myarray.fromfile(f, size)
    f.close()
elif test == 'L':
    myarray = array.array('L', [0] * size)
elif test == 'S':
    myarray = array.array('L', [0]) * size
elif test == 'I':
    myarray = array.array('L', ZeroIterable(size))
elif test == 'B':
    myarray = array.array('L', bytes(size * 8))
print(len(myarray))
print(time.time() - t)

'S'方法(array.array('L', [0]) * size)获胜:

$ python3 --version
Python 3.7.3
$ python3 z.py Z
100000000
1.1691830158233643
$ python3 z.py L
100000000
2.712920665740967
$ python3 z.py S
100000000
0.6910817623138428
$ python3 z.py B
100000000
0.9187061786651611
$ python3 z.py I
100000000
62.862160444259644

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