Question

I’m looking for an easy python way to compare column types from SQLAlchemy to base types. For example, if my column type is a VARCHAR of any length, I want to read it as a string.

I can read the column type okay, but I’m not sure an easy way to verify it’s basic type… it would be nice if I could use something like “if isinstance(mycolumn, int)” – but I’m new to python and not sure how this would work.

Here’s what I have so far:

from sqlalchemy import MetaData
from sqlalchemy import create_engine, Column, Table
engine = create_engine('mysql+mysqldb://user:pass@localhost:3306/mydb', pool_recycle=3600)
meta = MetaData()
meta.bind = engine
meta.reflect()
datatable = meta.tables['my_data_table']
[c.type for c in datatable.columns]

Output:

[INTEGER(display_width=11), DATE(), VARCHAR(length=127), DOUBLE(precision=None, scale=None, asdecimal=True)]

My end purpose is twofold, first because I want to format the output based on the type when I load it into my jQuery jqGrid. The second, is I’m slowly converting non-normalized data tables into a normalized structure, and want to ensure that I keep my types consistent – (to make sure my numbers in the previous table are stored as numbers and not strings…)

Answer 1

One solution is to do the conversion manually – for example, this works:

def convert(self, saType):
    type = "Unknown"
    if isinstance(saType,sqlalchemy.types.INTEGER):
        type = "Integer"
    elif isinstance(saType,sqlalchemy.types.VARCHAR):
        type = "String"
    elif isinstance(saType,sqlalchemy.types.DATE):
        type = "Date"
    elif isinstance(saType,sqlalchemy.dialects.mysql.base._FloatType):
        type = "Double"
    return type

Not sure if this is a normal python way of doing things… I still think like a java programmer.