Sqlalchemy binary data type
In order to specify SQLAlchemy column types, you will need to import the types module like this:. This section enumerates some of the more commonly used SQLAlchemy classes that are used to specify column types.
When you create a Columnyou can pass either a class name sqlalchemy binary data type an instance as the type argument. For a number of generic, simple data types like Integer or Dateyou'll generally specify the type as just a class name. For sqlalchemy binary data type types that need additional information, such as the size of a text field, you'll pass that additional information to the constructor, and use the resulting instance as the type argument to the Column constructor.
Suppose your database has a table named horses that describes horses. The first column is the horse's name, the primary key, up to 40 characters; and the second column is its birthdate. This code would add that table's description to a MetaData instance named meta ; note that the type of the first column is an instance of the Text class, while the type of the second column is the name of a class Date.
SQLAlchemy's types have two faces: Here are some of the more common data types. Refer to the vendor's documentation for the sqlalchemy binary data type set. Represents a Python bool value, True or False. Represents a calendar date as a datetime. Represents a date and time as a datetime.
Represents a floating-point number as a Python float. If you use the class name Float to sqlalchemy binary data type this type, you will get a column of the maximum precision. You may also specify an expression of this form to select the precision:.
The value of B is the number of bits of precision in the mantissa. In practical terms, any value of B from 1 to 24 will give you a single-precision float, while values 25—53 will give you a double-precision column. Represents a Python int integer. Some engines may not support values that would require a Python long. Represents an interval of time, which will use a Python datetime. Represents a scaled integer. Use an expression of this general form to specify a field of this type:.
The precision argument specifies the maximum number of decimal digits, and the scale argument specifies the scale factor. For example, a value of type Numeric 5,2 will hold numbers sqlalchemy binary data type up to five digits, but with an implied decimal point before the last two digits, that is, numbers up to The default scale value is zero, and the default precision value depends on the underlying database engine.
Represents a Python str or unicode value. For most engines, you must indicate the maximum length using a constructor call of sqlalchemy binary data type general form:. For Python str and unicode types. Values represent a time of day, and are represented on the Python side by an instance sqlalchemy binary data type the time class in the datetime module. Use this column type for Unicode strings. Passing str values to SQLAlchemy for this type is not recommended.
Use the types in this list to guarantee that the SQL type of the same name will be used. Use the class name e. FLOAT [ precision ]: A two-byte signed sqlalchemy binary data type value in the range [, ].
A variable-length text column whose maximum capacity is maxlen bytes. A binary string with a capacity of maxlen bytes. A case-insensitive character string with a capacity of maxlen bytes. Specifying a column's foreign key relation. Metadata for one table column.