[英]How can I parse this list of comma separated values
我有一个用逗号分隔的用户及其权限的列表,其中一些用户最多具有8个权限:
user_a, permission_1
user_b, permission_1, permission_2
user_c, permission_1, permission_2, permission_3
我需要输出以逗号分隔的用户和权限列表,其中每个用户和权限对都位于单独的行上:
user_a, permission_1
user_b, permission_1
user_b, permission_2
user_c, permission_1
user_c, permission_2
user_c, permission_3
我下面使用csv模块的python代码目前无法正常工作:
import csv
with open('user_list.csv') as user_list:
dict_reader = csv.DictReader(user_list)
ul = []
for row in dict_reader:
ul.append(row)
with open('output.txt','w') as output:
fields = 'USER','PERM1','PERM2','PERM3','PERM4',
'PERM5','PERM6','PERM7','PERM8'
dict_writer = csv.DictWriter(output, fields)
csv.DictWriter.writeheader(dict_writer)
for i in ul:
dict_writer.writerow(i)
它给了我以下回溯:
Traceback (most recent call last):
File "cops_ul_parse.py", line 15, in <module>
dict_writer.writerow(i)
File "C:\Python27\lib\csv.py", line 148, in writerow
return self.writer.writerow(self._dict_to_list(rowdict))
File "C:\Python27\lib\csv.py", line 144, in _dict_to_list
", ".join(wrong_fields))
ValueError: dict contains fields not in fieldnames: PERM8, PERM7, PERM6, PERM5
知道为什么这行不通吗? 或者,是否有更好的方法来完成所需的输出? 也许正则表达式会更好?
问题是此行:
fields = 'USER','PERM1','PERM2','PERM3','PERM4',
'PERM5','PERM6','PERM7','PERM8'
您的代码正在执行以下fields = 'USER','PERM1','PERM2','PERM3','PERM4',
(请记住,元组和列表的最后一项后面可以有逗号结尾),然后再创建另一个元组( 'PERM5','PERM6','PERM7','PERM8'
),并且对此不执行任何操作。
然后,当您创建csv.DictWriter
,它仅具有第一个元组中的字段-因此会出现错误。
解决方案很简单:在元组周围使用方括号,这样可以隐含地延续行:
fields = ('USER','PERM1','PERM2','PERM3','PERM4',
'PERM5','PERM6','PERM7','PERM8')
您也可以使用反斜杠来避开换行符,但是括号要好看得多。
for perm in listOfPermissions:
user, perms = perm.split(',', 1)
for p in perms:
print "%s, %s" %(user, p)
要将其写入文件:
with open('path/to/file', 'w') as outfile:
for perm in listOfPermissions:
user, perms = perm.split(',', 1)
for p in perms:
outfile.write("%s, %s\n" %(user, p))
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