python - 如何标记正则表达式模式并对结果列表进行排序？

Question

我有一个看起来像这样的文件:

select a,b,c FROM Xtable
select a,b,c FROM Vtable
select a,b,c FROM Atable
select a,b,c FROM Atable
select d,e,f FROM Atable

我想得到一个 sortedMap:

{
"Atable":["select a,b,c FROM Atable", "select d,e,f FROM Atable"],
"Vtable":["select a,b,c FROM Vtable"],
"Xtable":["select a,b,c FROM Xtable"]
}

sortedMap 的键是表名，值是列表中的文本行。

我从这个开始，但坚持对正则表达式匹配的行进行标记:

import re

f = open('mytext.txt', 'r')
x = f.readlines()
print x
f.close()
for i in x:
    p = re.search(".* FROM ", i)
 //now how to tokenize and get the value that follows FROM

Answer 1

您可以结合使用 defaultdict 和正则表达式。让 lines 成为你的线路列表:

from collections import defaultdict
pattern = "(select .+ from (\S+).*)"
results = defaultdict(list)

for line in lines:
     query, table = re.findall(pattern, line.strip(), flags=re.I)[0]
     results[table].append(query)

实际上，读取文件的正确方法是:

with open('mytext.txt') as infile:
    for line in infile:
         query, table = re.findall(pattern, line.strip(), flags=re.I)[0]
         results[table].append(query)

结果自然是一个 defaultdict。如果要将其转换为有序字典，调用字典构造函数:

from collections import OrderedDict
OrderedDict(sorted(results.items()))
#OrderedDict([('Atable', ['select a,b,c FROM Atable', ...

您可以使模式更健壮，以跟踪逗号、有效标识符等。