Fetching Columns from Table

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February 9th, 2012, 03:24 AM

desktoppc

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Fetching Columns from Table

hi ,

i am trying to fetch all column from a database table , but i am only able to fetch 1 column from table , here is a part of code which is fetching one column from table , i want to know ho can i display multiple columns

Code:

db += [(row ['fname'],str(row[ 'userid' ]), False),]

suppose i want to fetch other column say lname , how can do that.
thanks

February 9th, 2012, 10:17 AM

b49P23TIvg

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provide more information

We need more information to answer this question.

What sort of object is row? It's __getattribute__ method, for instance, might take funky behind-the-scene action.

Likewise, what is your db object? It might have some sort of weird (custom) __add__ method.

What's the database format?

Post a small example.

February 10th, 2012, 12:49 PM

desktoppc

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thanks

February 10th, 2012, 01:39 PM

b49P23TIvg

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Progress.

I think that we should not have to install psycopg2 or read the psycopg2 documents to answer your question.

We know now that db is a standard python list object.

result_set is probably an iterable collection of somethings.

row is those somethings, one at a time.

I suggest next you insert a few statements into your program to help. Run this modified program and report the output:

Code:

import pprint################################################################

def values_from_db():
    pkg_resources.require( "psycopg2" )
    engine = create_engine('postgresql://postgres:@127.0.0.1:5432/users')
    connection = engine.connect()
    result_set = connection.execute( "select * from concatenation(5,10,20)" )
    print(type(result_set))##################################################
    pprint.pprint(result_set)################################################
    db = []
    for row in result_set:
        db += [(row ['start'],str(row[ 'userdatadetailid' ]), False),]

    connection.close()

    return db

def __main__():
    values_from_db()#########################################################

if __name__ == "__main__": __main__()

February 10th, 2012, 02:03 PM

desktoppc

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over

February 10th, 2012, 02:35 PM

b49P23TIvg

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What is the error message? I cannot test my program. I don't have access to that web address.

concatenation

summary: + operator joins string, tuple, list types. The mutable types have additional choices, and dictionaries use the update method.

Code:

>>> ################################################################
>>> a='a'  # strings
>>> b='b'
>>> a+b
'ab'
>>> ''.join((a,b,))
'ab'
>>> ################################################################
>>> a=(1,) # tuples
>>> b=('B',)
>>> a+b
(1, 'B')
>>> ################################################################
>>> a = list(range(3))  # lists
>>> b=[c for c in 'cat']
>>> a+b
[0, 1, 2, 'c', 'a', 't']
>>> a.extend(b)      # (modifies a)
>>> a
[0, 1, 2, 'c', 'a', 't']
>>> ################################################################
>>> a = {1:'one','one':2}  # dictionary
>>> b = {i:j for (i,j,) in enumerate('KIT')}
b = {i:j for (i,j,) in enumerate('KIT')}
>>> a
{1: 'one', 'one': 2}
>>> b
{0: 'K', 1: 'I', 2: 'T'}
>>> a.update(b)  # alters a
>>> a
{0: 'K', 1: 'I', 2: 'T', 'one': 2}
>>>