Demonstrating JSON Schema validation, using multiple examples.

jsonschema_flask.py

from flask import Flask, jsonify, request
from jsonschema import Draft7Validator

app = Flask(__name__)
app.config["JSONIFY_PRETTYPRINT_REGULAR"] = True

schema = {
    "type": "object",
    "properties": {
        "hospital": {"type": "string"},
        "covid_tests": {
            "type": "object",
            "properties": {
                "amount": {"type": "number"},
                "positive": {"type": "number"},
                "from": {"type": "string", "format": "date"},
                "to": {"type": "string", "format": "date"}
            }
        }
    }
}

@app.route("/covid_data_validation", methods=["POST"])
def f_index():
    validator = Draft7Validator(schema)
    errors = {"errors": [e.message for e in validator.iter_errors(request.json)]}
    if errors["errors"]:
        return jsonify(errors), 400
    return "Data sucessfully validated!"
  
if __name__ == "__main__":
    app.run()

jsonschema_flask_sample_nok.json

{
    "hospital": "University of Mariland Medical Center",
    "covid_tests": {
        "amount": "300",
        "positive": 23,
        "from": "2020-09-01",
        "to": "2020-09-31"
    }
}

jsonschema_flask_sample_ok.json

{
    "hospital": "University of Texas MD Anderson Cancer Center",
    "covid_tests": {
        "amount": 564,
        "positive": 68,
        "from": "2020-09-01",
        "to": "2020-09-31"
    }
}

jsonschema_is_valid.py

from jsonschema import Draft7Validator                                              
                                                                                    
schema = {                                                                          
    "type": "object",                                                               
    "properties": {                                                                 
        "hospital": {"type": "string"},                                             
        "covid_tests": {                                                            
            "type": "object",                                                       
            "properties": {                                                         
                "amount": {"type": "number"},                                       
                "positive": {"type": "number"},                                     
                "from": {"type": "string", "format": "date"},                       
                "to": {"type": "string", "format": "date"}                          
            }                                                                       
        }                                                                           
    }                                                                               
}                                                                                   
                                                                                    
data = {                                                                            
    "hospital": "University of Mariland Medical Center",                            
    "covid_tests": {                                                                
        "amount": "300", # field expected to be number, will make is_valid() return False    
        "positive": 23,                                                             
        "from": "2020-09-01",                                                       
        "to": "2020-09-31"                                                          
    }                                                                               
}                                                                                   
                                                                                    
print(Draft7Validator(schema).is_valid(data))  

jsonschema_lazy_validation.py

from jsonschema import Draft7Validator                                              
                                                                                    
schema = {                                                                          
    "type": "object",                                                               
    "properties": {                                                                 
        "hospital": {"type": "string"},                                             
        "covid_tests": {                                                            
            "type": "object",                                                       
            "properties": {                                                         
                "amount": {"type": "number"},                                       
                "positive": {"type": "number"},                                     
                "from": {"type": "string", "format": "date"},                       
                "to": {"type": "string", "format": "date"}                          
            }                                                                       
        }                                                                           
    }                                                                               
}                                                                                   
                                                                                    
data = {                                                                            
    "hospital": "University of Mariland Medical Center",                            
    "covid_tests": {                                                                
        "amount": "300", # field expected to be number, will generate an error  
        "positive": 23,                                                             
        "from": "2020-09-01",                                                       
        "to": "2020-09-31"                                                          
    }                                                                               
}                                                                                   
                                                                                    
validator = Draft7Validator(schema)                                                 
                                                                                    
for error in validator.iter_errors(data):                                           
    print(f"Error: {error.message}")
    
print("Done!")

jsonschema_required_fields.py

from jsonschema import Draft7Validator

schema = {
    "type": "object",
    "properties": {
        "hospital": {"type": "string"},
        "covid_tests": {
            "type": "object",
            "properties": {
                "total_cases": {"type": "number"},
                "amount": {"type": "number"},
                "positive": {"type": "number"},
                "from": {"type": "string", "format": "date"},
                "to": {"type": "string", "format": "date"}
            },
            "required": ["amount", "positive", "from", "to"]
        }
    }
}

data = {
    "hospital": "University of Mariland Medical Center",
    "covid_tests": {      # amount field was removed intentionally
        "total_cases": 1526,
        "positive": 23,
        "from": "2020-09-01",
        "to": "2020-09-31"
    }
}

validator = Draft7Validator(schema)

for error in validator.iter_errors(data):
    print(f"Error: {error.message}")

print("Done!")

jsonschema_validate.py

from jsonschema import validate                                                     
                                                                                    
schema = {                                                                          
    "type": "object",                                                               
    "properties": {                                                                 
        "hospital": {"type": "string"},                                             
        "covid_tests": {                                                            
            "type": "object",                                                       
            "properties": {                                                         
                "amount": {"type": "number"},                                       
                "positive": {"type": "number"},                                     
                "from": {"type": "string", "format": "date"},                       
                "to": {"type": "string", "format": "date"}                          
            }                                                                       
        }                                                                           
    }                                                                               
}                                                                                   
                                                                                    
data = {                                                                                           
    "hospital": "University of Mariland Medical Center",                                           
    "covid_tests": {                                                                               
        "amount": "300", # field expected to be number, will throw Exception                       
        "positive": 23,                                                                            
        "from": "2020-09-01",                                                       
        "to": "2020-09-31"                                                          
    }                                                                               
}                                                                                   
                                                                                    
print(validate(instance=data, schema=schema))