Is ‘__tablename__’ Compulsory in SQLAlchemy? Can We Change It?

Is __tablename__ Compulsory in SQLAlchemy? Can We Change It?

No, __tablename__ is not compulsory, but it is highly recommended in SQLAlchemy when using the ORM (Object-Relational Mapping).

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What Does __tablename__ Do?

When you define a model in SQLAlchemy like this:

<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>__tablename__</span> <span>=</span> <span>"</span><span>users</span><span>"</span>  <span>#  Defines the table name </span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>__tablename__</span> <span>=</span> <span>"</span><span>users</span><span>"</span>  <span>#  Defines the table name </span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
class User(Base):
    __tablename__ = "users"  #  Defines the table name 
    id = Column(Integer, primary_key=True, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)

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• The __tablename__ sets the name of the table in the database.
• Without it, SQLAlchemy will automatically generate a table name based on the class name.

What Happens If We Don’t Use __tablename__?

If you don’t define __tablename__, SQLAlchemy will autogenerate a name based on the class.

Example Without __tablename__:

<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
class User(Base):
    id = Column(Integer, primary_key=True, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)

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Generated Table Name: "user" (lowercase version of the class name)

Can We Change __tablename__?

Yes! You can change it to any valid table name.

Example with a Custom Table Name:

<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>__tablename__</span> <span>=</span> <span>"</span><span>my_custom_users_table</span><span>"</span>  <span>#  Custom table name </span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
<span>class</span> <span>User</span><span>(</span><span>Base</span><span>):</span>
    <span>__tablename__</span> <span>=</span> <span>"</span><span>my_custom_users_table</span><span>"</span>  <span>#  Custom table name </span>
    <span>id</span> <span>=</span> <span>Column</span><span>(</span><span>Integer</span><span>,</span> <span>primary_key</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>)</span>
    <span>email</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>unique</span><span>=</span><span>True</span><span>,</span> <span>index</span><span>=</span><span>True</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
    <span>hashed_password</span> <span>=</span> <span>Column</span><span>(</span><span>String</span><span>,</span> <span>nullable</span><span>=</span><span>False</span><span>)</span>
class User(Base):
    __tablename__ = "my_custom_users_table"  #  Custom table name 
    id = Column(Integer, primary_key=True, index=True)
    email = Column(String, unique=True, index=True, nullable=False)
    hashed_password = Column(String, nullable=False)

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Now the table name will be: my_custom_users_table

When Should We Use __tablename__?

Final Answer:

• __tablename__ is not required, but recommended.
• You can change the table name to anything valid.
• If you don’t define it, SQLAlchemy will use the lowercase class name as the table name.

原文链接：Is ‘__tablename__’ Compulsory in SQLAlchemy? Can We Change It?