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RE: Python Newbie with a Python/MYSQL Question

Hi,
I'm a Python newbie. I have a pretty basic script that does a "select * from tablename" and returns two list of tuples. The format of my TEST database looks like this:

mysql> select * from employee;
+-----+--------+------------+--------+
| id  | name   | dept       |
+-----+--------+------------+--------+
| 100 | Thomas | Sales      |   
| 200 | Jason  | Technology |  
| 300 | Mayla  | Technology |

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I want to have the column match the first record in the row. For example, my first line would look like
id: 100 name: Thomas Dept: Sales
id:200 name: Jason Dept: Techology
id: 300 name: Mayla Dept: Technology

Here's the last bock of my code with output:

         cursor.execute("SELECT * FROM" + ' ' + table)

         data1=cursor.fetchall()

         cfields=[i[0] for i in cursor.description]

         return cfields,data1

    except:

         print "Error: unable to fetch data"

    db.close()

def ColumnFields():


    return cfields


def main():

    test1,test2=ConnectDb()

    print test1
    print test2

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Can someone please give me ideas on how to do this. Also, for some reason, when I print this out, I get an extra letter in my output for the second tuple. Why is this (the L shouldn't be there with the numbers)? Also, why is my first output a list and not a tuple? Thanks in advance!!

['id', 'name', 'dept', ]
((100L, 'Thomas', 'Sales'), (200L, 'Jason', 'Technology'), (300L, 'Mayla', 'Technology',), (400L, 'Nisha', 'Marketing'), (500L, 'Randy', 'Technology'))

SOLUTION

larsrohr

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pepr

Yes, larsrohr deserves his points :)

In 100L the L simply means that the long integer type is used by Python. You should not care about it. The long integer and the "normal" integer were merged in newer versions of Python. Think about it as about implementation detail.

He is right also with the list/tuple answer. The cfields = [i[0] for i in cursor.description] means that you are assigning the result of so called list comprehension to the cfields.

The equivalent code without using the list comprehension is:

    cfields = []    # init -- empty list
    for i in cursor.description:
        cfields.append(i[0])

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To dig deeper, the i[0] for i in cursor.description is a generator expression that returns iterator. The iterator goes through all values of i[0] where i goes through all values from another iterator returned by the cursor.description.

Try cfields = tuple([i[0] for i in cursor.description) instead (i.e. feed the tuple constructor with the results of the same generator expression instead of enclosing in the square brackets). In other words, the square brackets in the list comprehension could be viewed as a syntactic sugar for the cfields = list([i[0] for i in cursor.description)

A side note, the cursor.execute("SELECT * FROM" + ' ' + table) can be a bit simplified as cursor.execute('SELECT * FROM ' + table). Single quotes and double quotes have exactly the same meaning -- you can choose. There is no char type in Python 'x' is not a character like in the C language. It is only a single-letter string.

ASKER CERTIFIED SOLUTION

pepr

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unix_admin777

ASKER

Thanks for all of the help. The explanations were excellent as well.