Perl 到 Python：散列到嵌套字典和 cx_Oracle答案

【问题标题】：Perl to Python: hash to nested dictionary and cx_OraclePerl 到 Python：散列到嵌套字典和 cx_Oracle
【发布时间】：2012-12-07 19:19:08
【问题描述】：

在将数据从 Oracle 数据库读取到数组后，我需要将 perl 哈希转换为嵌套的键控 Python 字典。最有效的方法是什么？现有的 Perl 代码（我根本不懂 Perl）是这样的：

# read the data and place into a species hash (sphash) and a data hash (tmphash)
my (@lnarr, %sphash, %tmphash, $tmpln, $tmpsel, $x, $datetime) ;
while (@lnarr = $csr->fetchrow_array) {
  $datetime = $lnarr[4].'-'.$lnarr[5] ;
  $tmpln = join '_', $lnarr[8], $lnarr[9] ;
  $sphash{$lnarr[7]} = 'x';
  $tmphash{$lnarr[0].'_'.$lnarr[1].'_'.$lnarr[2].'_'.$lnarr[3].'_'.$datetime.'_'.$lnarr[6]}{$lnarr[7]} .= $tmpln ;
} #while line

我不确定创建嵌套字典的最有效途径是什么……任何指导都会很棒。

我的初始代码看起来像这样，但我知道它可能非常错误（我也只是在学习 python）：根据这篇文章，前几行是从 Oracle 输出中读取元组到字典中：here

#this is creating the dictionary from the data
cursor.execute(query, cruise6_input=cruise6_input)
desc=[d[0] for d in cursor.description]   
result=[dict(zip(desc,line)) for line in cursor]

station=[r['STATION'] for r in result]
time=[r['GMT_TIME']for r in result]
svspp=[r['SVSPP'] for r in result]
expcatchwt=[r['EXPCATCHWT'] for r in result]
beglat=[r['BEGLAT'] for r in result]
expcatchnum=[r['EXPCATCHNUM'] for r in result]
cruise=[r['CRUISE'] for r in result]
towdate=[r['BEGIN_GMT_TOWDATE'] for r in result]
stratum=[r['STRATUM'] for r in result]
beglon=[r['BEGLON'] for r in result]

tmpln=zip(expcatchwt,expcatchnum)
tmphash=zip(station,time,beglat,cruise,towdate,stratum,beglon)
keys=zip(tmphash,svspp)

如何获得 tmphash[svspp]=tmpln 的输出？如果我打印 tmphash[svspp] 结果就是 {}....

【问题讨论】：

标签： python perl dictionary cx-oracle

【解决方案1】：

在python字典项访问使用dictionary[key]；所以你需要更正sphash 和tmphash 的行：

sphash[result[7]] = 'x'
tmphash[result[0] + '_' + result[1] + '_' + result[2] + '_' + result[3] + '_' + datetime + '_' +
        result[6]][result[7]] = tmpln

这假设tmphash[somekey] 本身已经是一个字典。您可以将其定义为 defaultdict:

from collections import defaultdict

tmphash = defaultdict(dict)

现在每个tmphash 键在访问时自动成为另一个dict。

【讨论】：

编辑后的代码看起来如何？使用 set vs sphash 有什么好处？
@VictoriaPrice：由于您只使用 dict 来跟踪唯一键，因此使用集合更有效（无需存储所有 x 值）。

【解决方案2】：

尽我所能纠正你的 python 代码：

# I have no idear what this is suppose to do
# i guess you are trying to mimic the array assignment in
# the while loop...but I think you are doing it wrong, please update your
# poste so we can make sense of it
desc=[d[0] for d in cursor.description]
# makes a list of dicts with the entire desc array as key and one line as value?!?!
result=[dict(zip(desc,line)) for line in cursor]

tmphash = {}
spset=set() # if you want an spset instead of hash
while (True): # this should probably be a for loop with your array
    datetime="%s-%s" % results[4:6]
    tmpln='_'.join(result[8:10])
    # here you probberbly want to add to a set instead of making a hash mapping to something useless
    sphash[result[7]]='x'
    # or
    spset.add(result[7])
    # .= is a string concatination operator in perl
    # += can also concatinate strings in python
    tmphash['_'.join(result[0:4]+[datetime]+result[6:8]] += tmpln

【讨论】：