python一个用于两个嵌套for循环的线性代码

Question

How to get the desired result in python one liner ??

object_list=[{'applicationName': "ATM Monitoring",
                         'roamingDrop': "",
                         'noOfCustomer': None,
                         'ipAddress': "192.168.1.1",
                          'url': "www.google.co.in",},
             {'applicationName': None,
                         'roamingDrop': "",
                         'noOfCustomer': None,
                         'ipAddress': "192.168.1.1",
                          'url': "www.google.co.in",}]

Result required is to replace all None to ""

object_list=[{'applicationName': "ATM Monitoring",
                         'roamingDrop': "",
                         'noOfCustomer': "",
                         'ipAddress': "192.168.1.1",
                          'url': "www.google.co.in",},
             {'applicationName': "",
                         'roamingDrop': "",
                         'noOfCustomer': "",
                         'ipAddress': "192.168.1.1",
                          'url': "www.google.co.in",}]

Simple Function to make this happens is :

def simple():
    for object in object_list:
        for key, value in object.iteritems():
            if value:
                dict( object, **{key: value})
            else:
                dict(object, **{key: ''})

And Python one unsuccessful one liner:

[dict(object, **{key: value}) if value else dict(object, **{key: ''}) 
    for object in object_list  for key, value in object.iteritems()]

Can the one liner be achieved with list comprehensions?

Answer 1

lst=[{'applicationName': "ATM Monitoring",
                     'roamingDrop': "",
                     'noOfCustomer': None,
                     'ipAddress': "192.168.1.1",
                      'url': "www.google.co.in",},
         {'applicationName': None,
                     'roamingDrop': "",
                     'noOfCustomer': None,
                     'ipAddress': "192.168.1.1",
                      'url': "www.google.co.in",}]

print [{key: val if val else "" for key, val in dct.items()} for dct in lst]

explained:

dct = lst[0]
{'applicationName': "ATM Monitoring",
                     'roamingDrop': "",
                     'noOfCustomer': None,
                     'ipAddress': "192.168.1.1",
                      'url': "www.google.co.in",}

Using dictionary comprehension (available since Python 2.7), first just reconstructing the dictionary into the same value:

{key: val  for dct.items()}

and extending it by assigning "" in case, we have as original value None (or any other value evaluating to False)

{key: val if val else ""  for dct.items()}

Finally (as shown above) it is applied in enveloping list comprehension to all items in the list.

{key: val  for dct.items()}

Strictly speaking, this replaces anything, what looks as boolean False by "".

If we want only None values replaced by "" , and eg False and 0 keep as it is, we shall e more strict:

print [{key: val if val is not None else "" for key, val in dct.items()} for dct in lst]

Answer 2

This seems easy enough:

>>> for d in object_list:
...     for k, v in d.items():
...         if v is None:
...             d[k] = ''
... 

and to show what the output looks like:

>>> import pprint
>>> pprint.pprint(object_list)
[{'applicationName': 'ATM Monitoring',
  'ipAddress': '192.168.1.1',
  'noOfCustomer': '',
  'roamingDrop': '',
  'url': 'www.google.co.in'},
 {'applicationName': '',
  'ipAddress': '192.168.1.1',
  'noOfCustomer': '',
  'roamingDrop': '',
  'url': 'www.google.co.in'}]