What about using if/else?

mastercounter = 0
phdcounter = 0
nodeegreecounter = 0

for candidate in response["person"]:
    if item["Degree"]:
        if item["Degree"]["key"] == "Master":
            mastercounter = mastercounter + 1
        if item["license"]["key"] == "PhD":
            phdcounter = phdcounter + 1
    else: 
       nodegreecounter = nodegreecounter + 1

You don't need the intricate tests on wether 'text' is present for the post caption. This code works well with the JSON string you posted:

for post in data['data']:
    if post.get('caption'):
        print post['caption'].get('text', 0)

Furthermore, you could be more defensive and refer to data.get('data', []) when starting the loop in case Instagram sends you empty JSON.

Check both, the key existence and its length:

import json, sys

obj=json.load(sys.stdin)

if not 'results' in obj or len(obj['results']) == 0:
    exit(0)
else:
    exit(1)

I think you mean if instead of for:

def parse_classes(json_data):
    lst = set()
    if 'classes' in json_data['images'][0]['classifiers'][0]:
        for item in json_data['images'][0]['classifiers'][0]['classes']:
            lst.add(item['class'])
    else:
        print("")
    return lst

or defensively

def parse_classes(json_data):
    lst = set()
    if (json_data.get('images')
            and json_data['images'][0].get('classifiers')
            and json_data['images'][0]['classifiers'][0].get('classes')):
        for item in json_data['images'][0]['classifiers'][0].get('classes', []):
            lst.add(item['class'])
    return lst if lst else None

if you want all class in all classifiers in all images

def parse_classes(json_data):
    lst = set()
    for image in json_data.get('images', []):
        for classifier in image.get('classifiers', []):
            for item in classifier.get('classes', []):
                lst.add(item['class'])
    return lst if lst else None

import json

jsonData = """{"from": {"id": "8", "name": "Mary Pinter"}, "message": "How ARE you?", "comments": {"count": 0}, "updated_time": "2012-05-01", "created_time": "2012-05-01", "to": {"data": [{"id": "1543", "name": "Honey Pinter"}]}, "type": "status", "id": "id_7"}"""

def getTargetIds(jsonData):
    data = json.loads(jsonData)
    if 'to' not in data:
        raise ValueError("No target in given data")
    if 'data' not in data['to']:
        raise ValueError("No data for target")

    for dest in data['to']['data']:
        if 'id' not in dest:
            continue
        targetId = dest['id']
        print("to_id:", targetId)

Output:

In [9]: getTargetIds(s)
to_id: 1543

Define a set of values that should be replaced with None and use list comprehension to "replace" them:

>>> string_list = [ "foo",1,None, "null","[]","bar"]
>>> none_items = {"null", "[]"}  # or set(("null", "[]"))
>>> [None if item in none_items else item for item in string_list]
['foo', 1, None, None, None, 'bar']

Or, use map():

>>> map(lambda x: None if x in none_items else x, string_list)
['foo', 1, None, None, None, 'bar']

Using set because of O(1) lookups.

"example" in data.keys() will return True or False, so this would be one way to check.

So, given JSON like this...

  { "example": { "title": "example title"}}

And given code to load the file like this...

import json

with open('example.json') as f:

    data = json.load(f)

The following code would return True or False:

x = "example" in data   # x set to True
y = "cheese" in data    # y set to False

You should also maybe check if the body key is actually there.

def checkJson(jsonContents):
    bodyFlag = True if "body" in jsonContents["objects"][0]["data"] and jsonContents["objects"][0]["data"]["body"] == "Present" else False
    codeFlag = True if "code" in jsonContents["objects"][0]["data"] and jsonContents["objects"][0]["data"]["code"] == 200 else False

    return bodyFlag or codeFlag

print checkJson(result)

The preferred way, when applicable:

for r in results:
     print r.get('key_name')

this will simply print None if key_name is not a key in the dictionary. You can also have a different default value, just pass it as the second argument:

for r in results:
     print r.get('key_name', 'Missing: key_name')

If you want to do something different than using a default value (say, skip the printing completely when the key is absent), then you need a bit more structure, i.e., either:

for r in results:
    if 'key_name' in r:
        print r['key_name']

or

for r in results:
    try: print r['key_name']
    except KeyError: pass

the second one can be faster (if it's reasonably rare than a key is missing), but the first one appears to be more natural for many people.

You should use the built-in json module, which was designed explicitly for this task:

>>> import json
>>> data = '''
... {
...   "abc": null,
...   "def": 9
... }
... '''
>>> json.loads(data)
{'def': 9, 'abc': None}
>>> type(json.loads(data))
<class 'dict'>
>>>

By the way, you should use this method even if your JSON data contains no null values. While it may work (sometimes), ast.literal_eval was designed to evaluate Python code that is represented as a string. It is simply the wrong tool to work with JSON data.