問題描述

我嘗試重寫一些 csv 讀取代碼，以便能夠在 Python 3.2.2 的多個內核上運行它.我嘗試使用多處理的 Pool 對象，該對象是我從工作示例中改編而來的(并且已經為我的項目的另一部分工作).我遇到了一條難以解讀和排除故障的錯誤消息.

I tried to rewrite some csv-reading code to be able to run it on multiple cores in Python 3.2.2. I tried to use the Pool object of multiprocessing, which I adapted from working examples (and already worked for me for another part of my project). I ran into an error message I found hard to decipher and troubleshoot.

錯誤:

Traceback (most recent call last):
  File "parser5_nodots_parallel.py", line 256, in <module>
    MG,ppl = csv2graph(r)
  File "parser5_nodots_parallel.py", line 245, in csv2graph
    node_chunks)
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/multiprocessing/pool.py", line 251, in map
    return self.map_async(func, iterable, chunksize).get()
  File "/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/multiprocessing/pool.py", line 552, in get
    raise self._value
AttributeError: __exit__

相關代碼:

import csv
import time
import datetime
import re
from operator import itemgetter
from multiprocessing import Pool
import itertools

def chunks(l,n):
    """Divide a list of nodes `l` in `n` chunks"""
    l_c = iter(l)
    while 1:
        x = tuple(itertools.islice(l_c,n))
        if not x:
            return
        yield x

def csv2nodes(r):
    strptime = time.strptime
    mktime = time.mktime
    l = []
    ppl = set()
    pattern = re.compile(r"""[A-Za-z0-9"/]+?(?=[,
])""")
    for row in r:
        with pattern.findall(row) as f:
            cell = int(f[3])
            id = int(f[2])
            st = mktime(strptime(f[0],'%d/%m/%Y'))
            ed = mktime(strptime(f[1],'%d/%m/%Y'))
        # collect list
        l.append([(id,cell,{1:st,2: ed})])
        # collect separate sets
        ppl.add(id)
    return (l,ppl)

def csv2graph(source):
    MG=nx.MultiGraph()
    # Remember that I use integers for edge attributes, to save space! Dic above.
    # start: 1
    # end: 2
    p = Pool()
    node_divisor = len(p._pool)
    node_chunks = list(chunks(source,int(len(source)/int(node_divisor))))
    num_chunks = len(node_chunks)
    pedgelists = p.map(csv2nodes,
                       node_chunks)
    ll = []
    ppl = set()
    for l in pedgelists:
        ll.append(l[0])
        ppl.update(l[1])
    MG.add_edges_from(ll)
    return (MG,ppl)

with open('/Users/laszlosandor/Dropbox/peers_prisons/python/codetenus_test.txt','r') as source:
    r = source.readlines()
    MG,ppl = csv2graph(r)

解決此問題的好方法是什么?

What's a good way to troubleshoot this?

推薦答案

問題出在這一行:

with pattern.findall(row) as f:

您正在使用 with 語句.它需要一個帶有 __enter__ 和 __exit__ 方法的對象.但是pattern.findall返回一個list，with試圖存儲__exit__方法，但是找不到它，并引發錯誤.只需使用

You are using the with statement. It requires an object with __enter__ and __exit__ methods. But pattern.findall returns a list, with tries to store the __exit__ method, but it can't find it, and raises an error. Just use

f = pattern.findall(row)

改為.

這篇關于如何對“AttributeError: __exit__"進行故障排除在 Python 中進行多處理?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！