Welcome

Introduction to MongoDB in Python

Donny Winston

Instructor

JavaScript Object Notation (JSON)

Objects {}

String keys & values {'key1':value1, 'key2':value2,...}
Order of values is not important

    {
    'id': 12345,
    'name': 'Donny Winston',
    'instructor': true    
    },

Arrays []

Series of values [value1, value2,...]
Order of values is important

[
 "instructor_1",
 "instructor_2",
 ...
]

JavaScript Object Notation (JSON)

{
  'people': [
    { 'id': 12345,
      'name': 'Donny Winston',
      'instructor': true,
      'tags': ['Python', 'MongoDB']        
    },

    { 'id': 54321
      'name': 'Guido van Rossum'
      'instructor':false
      'tags': null
    },    
  ]
}

Values

Strings 'name':'Donny Winston'
Numbers 'id': 12345
true/false
null
Another array
```
'tags': ['Python', 'MongoDB'] 
```
Another object
```
  [{ 'id': 12345,  ...},...]
```

JSON <> Python

JSON	Python
Objects	Dictionaries `dict`
Arrays	Lists `list`
Values:
· strings	`str`
· _numbers _	`int`, `float`
·`true`/`false`	`True`/`False`
· `null`	`None`
· other objects/arrays	other `dict`/`list`

JSON <> Python <> MongoDB

MongoDB	JSON	Python
Databases	Objects	Dictionaries
↳Collections	Arrays	Lists
↳↳Documents	Objects	Dictionaries
↳↳↳Subdocuments	Objects	Dictionaries
↳↳↳ Values	Value types	Value types + `datetime`, regex...

mongodb database structure

The Nobel Prize API data(base)

import requests
from pymongo import MongoClient

# Client connects to "localhost" by default
client = MongoClient()
# Create local "nobel" database on the fly
db = client["nobel"]


for collection_name in ["prizes", "laureates"]:
    # collect the data from the API
    response = requests.get(
        "http://api.nobelprize.org/v1/{}.json".\
      format(collection_name[:-1] ))
    # convert the data to json
    documents = response.json()[collection_name]
    # Create collections on the fly
    db[collection_name].insert_many(documents)

structure of the nobel database

Accessing databases and collections

Using []

# client is a dictionary of databases
db = client["nobel"]

# database is a dictionary of collections
prizes_collection = db["prizes"]

Using .

# databases are attributes of a client
db = client.nobel

# collections are attributes of databases
prizes_collection = db.prizes

structure of the nobel database

Count documents in a collection

# Use empty document {} as a filter
filter = {}

# Count documents in a collection
n_prizes = db.prizes.count_documents(filter)
n_laureates = db.laureates.count_documents(filter)

590
934

# Find one document to inspect
doc = db.prizes.find_one(filter)

{'_id': ObjectId('5bc56145f35b634065ba1996'),
 'category': 'physics',
 'laureates': [{'firstname': 'Arthur',
   'id': '960',
   'motivation': '"for the optical tweezers and their 
   application to biological systems"',
   'share': '2',
   'surname': 'Ashkin'},
  {'firstname': 'Gérard',
   'id': '961',
   'motivation': '"for their method of generating 
   high-intensity, ultra-short optical pulses"',
  ...

Let's practice!

Introduction to MongoDB in Python