Implementing db querying

back/db.py

@@ -0,0 +1,85 @@
+from sqlalchemy import Column, Table, Integer, MetaData, String, select, create_engine
+from sqlalchemy.sql import func
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.ext.declarative import declarative_base
+
+
+SQLALCHEMY_DATABASE_URL = "sqlite:///./sql_app.db"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False}
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+Base = declarative_base()
+
+
+class People(Base):
+    __tablename__ = "people"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String)
+    age = Column(Integer)
+    gender = Column(String)
+    country = Column(String)
+
+
+def create_people_from_list(db, people_list):
+    count = 0
+    for p in people_list:
+        db_people = People(**p.dict())
+        db.add(db_people)
+        count += 1
+
+    db.commit()
+    return count
+
+
+def get_average_age_by_country(db) -> []:
+    return db.query(People.country.label('country'), func.avg(People.age).label('average_age'))\
+             .group_by( People.country).all()
+
+
+def count_people_by_country(db) -> []:
+    return db.query(People.country.label('country'), func.count(People.id).label('people_count'))\
+             .group_by( People.country).all()
+
+
+def get_gender_repartition_by_country(db, country) -> []:
+    count_women, total = db.query(
+
+        select(func.count(People.id).label('count_women')) \
+        .where(People.gender == 'F') \
+        .where(People.country == country).subquery(),
+
+        select(func.count(People.id).label('total')) \
+        .where(People.country == country).subquery(),
+
+    ).first()
+    female_proportion = count_women / total
+    return {
+        "female_proportion": female_proportion,
+        "male_proportion": 1 - female_proportion
+    }
+
+
+meta = MetaData()
+Table(
+    'people', meta,
+    Column('id', Integer, primary_key=True),
+    Column('name', String),
+    Column('age', Integer),
+    Column('gender', String),
+    Column('country', String),
+)
+meta.create_all(engine)