Creating Tables from a Schema defined in YAML

[monosij...@gmail.com]

Hello - Wondering if someone could please help me with this:

I have created a schema definition file in YAML which I read into a dict.

I am used to statically creating a table in this form:

tableName = Table (theTableName, Metadata, 

Column(column1, String),

Column(column2, String),

Column(coulumn3, String)

...

)

I am trying to see if there is a way to dynamically create a table using the column definition in the YAML file. So it would need to iterate over the column names and the types.

I tried with creating the string = 'Column(column1, String), Column(column2, String), Column(coulumn3, String) ...'

by iterating over the dict keys and then calling as above - but that did not work.

Just wondering if there would be another way to do this.

I looked at mapper as well but then that is for objects.

Thanks.

Mono

[Kevin Horn]

The answer to this probably depends on exactly what your schema looks like, but based on what you've told us so far, I would probably try to create all the columns first, get them into a list or tuple, and then use "star args" to pass them into the Table constructor.  Something like this:

columns = [Column(name, type) for name, type in some_kind_of_iterable_generated_from_your_yaml]

table = Table(theTableName, Metadata, *columns)

though obviously that's a very rough example

--

Kevin Horn

[Monosij Dutta-Roy]

Hi Kevin -

Thanks for your help. I am, however, unable to call Column on the tuple (attrname, 'String').

I tried like this:

columns = []

for attribute in attrList:

tup = attribute, 'String'

tupC = Column(tup)   // does not work

columns.append(tup)

So Columns (tup) did not work and I also tried calling Column on the tuples list I created in the iterator.

So my call to create a table as in:

theTable = Table (tableName, Metadata, *columns) - does not work. I also tried w/o the column call but did not expect it to work.

So sounds like would be a 'star args' for the Column call as well but am unable to find it.

Please let me know if I am approaching this incorrectly (I assume I am).

Also, I could generate a SQL create statement from my YAML file.

Would there be a way to use the Table command to create a table from that - but it would defeat the purpose as if go with a different DBMS I have to make sure the SQL is addressed? Or does sqlalchemy take care of that as well?

If there is some documentation you could refer me to in how this dynamic generation is implemented will be great.

Also, since it is a tuple I assume I can put in PK / FK information as well.

And I can help create some of this documentation if it does not exist. Its a great library, very helpful, just trying to find some flexibility.

Thank you for your help.

Mono

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