check for None in an array in flask (jinja template)

问题

I have a weird situation where array has value as None:

'synonyms': [None]

The json format of data in mongo is as:

{
    "_id": {
        "$oid": "5e0983a63bcf0dab51f32a9d"
    },
    "word": "vulgarizer",
    "wordset_id": "c0c349060a",
    "labels": [{
        "name": "American",
        "is_dialect": true
    }],
    "meanings": [{
        "id": "3cb39b55e5",
        "def": "someone who makes attractive to the general public",
        "speech_part": "noun",
        "synonyms": ["populariser"]
    }, {
        "id": "865bfdea0b",
        "def": "someone who makes something vulgar",
        "speech_part": "noun",
        "synonyms": [null]
    }],
    "editors": ["lefurjah"],
    "contributors": ["luxfactaest", "msingle", "bryanedu"]
}

But when I tried printing the same in python it showed up as:

'meanings': [{
    'id': '3cb39b55e5',
    'def': 'someone who makes attractive to the general public',
    'speech_part': 'noun',
    'synonyms': ['populariser']
}, {
    'id': '865bfdea0b',
    'def': 'someone who makes something vulgar',
    'speech_part': 'noun',
    'synonyms': [None]
}]

How do I check this value in if condition :

I have tried as:

{% if meaning['synonyms'] is defined and meaning['synonyms']|length > 0 %}
    do something-- if condition matches

But the None in array doesn't refer to a null value ?

Any possible solution? TIA

回答1:

You can use in condition inside jinja (as in Python).

from jinja2 import Template

data = {"synonyms": [None], "synonyms2": ['ok']}
tm = Template(
    "None in synonyms: {{ None in data['synonyms'] }}\n"
    "None in synonyms2: {{ None in data['synonyms2'] }}\n"
    "{% if None in data['synonyms'] %}None in synonyms {% endif %}\n"
    "{% if None in data['synonyms2'] %}None in synonyms2 {% endif %}\n"
)
msg = tm.render(data=data)
print(msg)

Result:

None in synonyms: True
None in synonyms2: False
None in synonyms

Hope this helps.

来源：https://stackoverflow.com/questions/59665771/check-for-none-in-an-array-in-flask-jinja-template

标签

Flask

jinja2