Again: virtual field requires type-attribute

[Martin Weissenboeck]

I have tried another model:

db.define_table('test',

    Field('t1'),

    Field('t2'),

    )

db.test.c12 = Field.Virtual (lambda r: r.t1+r.t2)

And i get:

<type 'exceptions.AttributeError'> 'FieldVirtual' object has no attribute 'type'

Version

web2py™(2, 4, 1, 'alpha.2', datetime.datetime(2013, 2, 17, 11, 27, 22))

PythonPython 2.7.1

	: H:\Python27\python.exe (prefix: H:\Python27)

What is wrong?

Regards, Martin

[Donatas Burba]

I have a workaround for this issue. Just a little helper function in modules:

def virtual_field(db, table_name, field_name, field_type, compute=lambda row: None, label='', represent=None):

    db[table_name][field_name] = Field.Virtual(compute)

    db[table_name][field_name].type = field_type

    db[table_name][field_name].label = label

    db[table_name][field_name].represent = represent

    db[table_name][field_name].formatter = lambda value: value

    db[table_name][field_name].comment = None

    db[table_name][field_name].readable = True

    db[table_name][field_name].writable = False

    db[table_name][field_name].requires = None

    db[table_name][field_name].widget = None

    db[table_name][field_name].name = field_name

    db[table_name][field_name].tablename = table_name

    db[table_name][field_name].filter_out = None

Because I very often need such virtual fields (to show complex computed result from several fields or even tables), this really helps me.

[Massimo Di Pierro]

This helped me a lot. I included these defaults in web2py so that you should need to do it yourself. Can you please check if 

db.test.c12 = Field.Virtual (lambda r: r.t1+r.t2)

now works as expected?

[Martin Weissenboeck]

Sorry, no - same message.
I have taken the last version from trunk one hour ago.

Ticket ID

127.0.0.1.2013-02-26.21-39-35.e1477239-8991-4217-810f-9e320daf692c

<type 'exceptions.AttributeError'> 'FieldVirtual' object has no attribute 'type'

Version

web2py™	(2, 4, 1, 'alpha.2', datetime.datetime(2013, 2, 25, 23, 19, 14))
Python	Python 2.7.3: D:\Python27\python.exe (prefix: D:\Python27)

Traceback

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

Traceback (most recent call last): File "D:\web2py\gluon\restricted.py", line 212, in restricted exec ccode in environment File "D:/web2py/applications/calctest/controllers/default.py", line 88, in <module> File "D:\web2py\gluon\globals.py", line 193, in <lambda> self._caller = lambda f: f() File "D:/web2py/applications/calctest/controllers/default.py", line 16, in t db.test.c12, File "D:\web2py\gluon\dal.py", line 9754, in select return adapter.select(self.query,fields,attributes) File "D:\web2py\gluon\dal.py", line 2218, in select return super(SQLiteAdapter, self).select(query, fields, attributes) File "D:\web2py\gluon\dal.py", line 1665, in select sql = self._select(query, fields, attributes) File "D:\web2py\gluon\dal.py", line 1520, in _select sql_f = ', '.join(map(geoexpand, fields)) File "D:\web2py\gluon\dal.py", line 1517, in geoexpand if isinstance(field.type,str) and field.type.startswith('geometry'): AttributeError: 'FieldVirtual' object has no attribute 'type'

2013/2/26 Massimo Di Pierro <massimo....@gmail.com>

--
 

[Massimo Di Pierro]

I get:

$ python web2py.py -S welcome

Version 2.4.1-alpha.2+timestamp.2013.02.26.11.40.15

Database drivers available: SQLite(sqlite3), MySQL(pymysql), PostgreSQL(pg8000), IMAP(imaplib)

WARNING:web2py:import IPython error; use default python shell

Python 2.7.1 (r271:86832, Jul 31 2011, 19:30:53) 

[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)] on darwin

Type "help", "copyright", "credits" or "license" for more information.

(InteractiveConsole)

>>> db.define_table('test',

...     Field('t1'),

...     Field('t2'),

...     )

<Table test (id,t1,t2)>

[Martin Weissenboeck]

My try:

db.define_table('test',
    Field('t1'),
    Field('t2'),
    )
   

db.test.c12 = Field.Virtual (lambda r: r.t1+r.t2)

def t():
    return dict(f=db(db.test.id>0).select(
        db.test.c12,
        ),
        c=db.test(1).c12,
        )

New version, new message:

Ticket ID

127.0.0.1.2013-02-26.22-38-37.30eb0659-ae50-4985-b105-f7303ce6b911

<class 'sqlite3.OperationalError'> near "<": syntax error

Version

web2py™	(2, 4, 1, 'alpha.2', datetime.datetime(2013, 2, 26, 11, 40, 15))

Python	Python 2.7.3: D:\Python27\python.exe (prefix: D:\Python27)

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[Martin Weissenboeck]

And here is the full traceback:

Traceback

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

21. 22.

Traceback (most recent call last

): File "D:\dropbox\InfoSMS\web2py\gluon\restricted.py", line 212, in restricted exec ccode in environment File "D:/dropbox/InfoSMS/web2py/applications/calctest/controllers/default.py", line 91, in <module> File "D:\dropbox\InfoSMS\web2py\gluon\globals.py", line 193, in <lambda>

self._caller = lambda f: f

() File "D:/dropbox/InfoSMS/web2py/applications/calctest/controllers/default.py", line 19, in t db.test.e12, File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 9765, in select return adapter.select(self.query,fields,attributes) File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 2218, in select

return super(SQLiteAdapter, self).select(query, fields, attributes

) File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 1678, in select return self._select_aux(sql,fields,attributes) File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 1643, in _select_aux self.execute(sql) File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 1756, in execute return self.log_execute(*a, **b) File "D:\dropbox\InfoSMS\web2py\gluon\dal.py", line 1750, in log_execute ret = self.cursor.execute(*a, **b) OperationalError: near "<": syntax error

Error snapshot

<class 'sqlite3.OperationalError'>(near "<": syntax error)

2013/2/26 Martin Weissenboeck <mwei...@gmail.com>

[Massimo Di Pierro]

>>> db = DAL()

>>> db.define_table('test',Field('t1'),Field('t2'))

<Table test (id,t1,t2)>

>>> db.test.c12 = Field.Virtual (lambda r: r.test.t1+r.test.t2)

>>> db.test.insert(t1='x',t2='y')

1L

>>> db.test(1).c12

'xy'

Notice:

db.test.c12 = Field.Virtual (lambda r: r.test.t1+r.test.t2)

not 

db.test.c12 = Field.Virtual (lambda r: r.t1+r.t2)

Moreover this is not valid:

db(db.test.id>0).select(db.test.c12)

you cannot select a virtual field from database. You can select the fields required to compute the virtual fields:

db(db.test.id>0).select(db.test.t1, db.test.t2)

and you get virtual field automatically:

for row in db(db.test.id>0).select(db.test.t1, db.test.t2): print row.c12

[Martin Weissenboeck]

Thank you for your help - now it works perfect!

[Julio del Barrio]

Hi, Massimo.
If I not want any virtual fields in row object returned by select? If I use the row as dict in a insert operation, I must to filter, and I haven't any way to know what field is virtual, in abstract.

[Massimo Di Pierro]

In select(....) you can pass the list of fields that you want. Are you asking for an automated way to exclude virtual fields?

[Anthony]

On Tuesday, July 19, 2016 at 3:54:10 PM UTC-4, Julio del Barrio wrote:

Hi, Massimo.
If I not want any virtual fields in row object returned by select? If I use the row as dict in a insert operation, I must to filter, and I haven't any way to know what field is virtual, in abstract.

If using an existing Row or dictionary in an insert, you should use the ._filter_fields method (which will also filter out the "id" field):

db.mytable.insert(**db.mytable._filter_fields(row))

Anthony