理解期間列表中的python類型

Question

我有一個如下的sql查詢字符串：

intro text,
id int,
description varchar(50)

我正在嘗試創建一個類型字符串，目的是查找與sql模式中定義的類型不匹配的文本。 我從sql文本中提取類型的方式如下：

types = [re.sub('[^a-zA-Z]','',x.split()[1]) for x in schema] 
types = [re.sub('varchar',types.StringType,x) for x in types]
types = [re.sub('text',types.StringType,x) for x in types]
types = [re.sub('bigint',types.IntType,x) for x in types]
types = [re.sub('decimal',types.IntType,x) for x in types]

但是口譯員抱怨說

types = [re.sub('varchar',types.StringTypes,x) for x in types]
AttributeError: 'list' object has no attribute 'StringTypes'

SSCCE

使用以下架構文件

intro text,
id int,
description varchar(50)

和代碼（注意，如下面的奧斯卡建議的那樣已修復，但現在有其他錯誤）

import csv
import sys
import re
import types

sch = open(sys.argv[1], "rb")

#---------------------------------   
# read schema
#---------------------------------     
with sch as f:
    schema = f.read().splitlines()

#---------------------------------    
# extract schema types
#---------------------------------  

foundtypes = [re.sub('[^a-zA-Z]','',x.split()[1]) for x in schema] 
foundtypes = [re.sub('varchar',str,x) for x in foundtypes]
foundtypes = [re.sub('text',str,x) for x in foundtypes]
foundtypes = [re.sub('int',int,x) for x in foundtypes]
foundtypes = [re.sub('bigint',int,x) for x in foundtypes]
foundtypes = [re.sub('decimal',int,x) for x in foundtypes]

print foundtypes

我正在使用Python 2.7.5

謝謝

Answer 1

在這一行中，您將綁定重寫（參見： variable shadowing ）到types 模塊 ：

types = [re.sub('[^a-zA-Z]','',x.split()[1]) for x in schema]

之后， types不再指向模塊，而是指向列表。 只需在所有作業中使用另一個名稱即可：

my_types = [re.sub('[^a-zA-Z]','',x.split()[1]) for x in schema] 
my_types = [re.sub('varchar',types.StringType,x) for x in my_types]
my_types = [re.sub('text',types.StringType,x) for x in my_types]
my_types = [re.sub('bigint',types.IntType,x) for x in my_types]
my_types = [re.sub('decimal',types.IntType,x) for x in my_types]

更新

我認為您對解決方案進行了過度設計，除了第一行以外，這不適合使用正則表達式。 一個簡單的if-elif-else可以正常工作：

def transform(typestr):
    if typestr in ('varchar', 'text'):
        return types.StringType
    elif typestr in ('int', 'bigint', 'decimal'):
        return types.IntType
    else:
        return None

my_types = [re.sub(r'[^a-zA-Z]', '', x.split()[1]) for x in schema] 
[transform(x) for x in my_types]
=> [<type 'str'>, <type 'int'>, <type 'str'>]

Answer 2

您正在覆蓋模塊types模塊。 更改要保存到的列表的名稱，它應該可以使用。

foundtypes = [re.sub('[^a-zA-Z]','',x.split()[1]) for x in schema] 
foundtypes = [re.sub('varchar',types.StringType,x) for x in foundtypes]
foundtypes = [re.sub('text',types.StringType,x) for x in foundtypes]
foundtypes = [re.sub('bigint',types.IntType,x) for x in foundtypes]
foundtypes = [re.sub('decimal',types.IntType,x) for x in foundtypes]