Syntax Error exec-ing python code from database

Question

I'm loading some python code from a database (it's doing dynamic mapping of values that I can change at runtime without a code redeploy).

In my code, I'm doing this to execute the database code:

if lMapping:
  print lMapping
  exec lMapping
  lValue = mapping(lValue, lCsvRow)

and here's the value of lMapping:

def mapping(pValue, pCsvRow):
  lInterimStatus = pCsvRow[5]
  lOutComeStatus = pCsvRow[6]

  if len(lInterimStatus) == 0:
    lStatus = lOutComeStatus
  else:
    lStatus = lInterimStatus

  lStatus = lStatus.lower()

  PRIMARY_STATUS_MAPPINGS = {
    'completed with lender' : '4828',
    'not taken up' : '4827',
    'declined across all lenders' : '4726',
    'declined broker duplicate' : '4726',
    'pending' : '4725',
    'pending (in progress with broker)' : '4725',
    'pending (in progress with lender)' : '4725',
    'lender accept in principle' : '4827',
    'lender decline duplicate' : '4743',
    'lender decline post code not supported' : '4743',
    'lender decline score fail' : '4743',
    'lender decline policy fail' : '4743',
    'lender decline no client contact' : '4743',
    'lender decline general' : '4743',
    'lender decline bad data' : '4743',
  }

  return PRIMARY_STATUS_MAPPINGS[lStatus]

Whenever I do this I'm getting a syntax error on the exec line, I can't work out why:

(<type 'exceptions.SyntaxError'>:invalid syntax (<string>, line 1)

UPDATE

It works if I write the code from the database to a file first:

print lMapping
lFile = open('/mapping.py','w')
lFile.write(lMapping)
lFile.close()
lReadFile = open('/mapping.py')
exec lReadFile
lValue = mapping(lValue, lCsvRow)

Answer 1

Do you BLOB or other binary type column to store code? Otherwise database might change line endings and exec will break with SyntaxError:

>>> s='''\
... print 'ok'
... '''
>>> s
"print 'ok'\n"
>>> exec s
ok
>>> exec s.replace('\n', '\r\n')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1
    print 'ok'
              ^
SyntaxError: invalid syntax

Update: Writing to file on Windows in text mode will change line endings to platform native ones. Another way to normalize them is:

lMapping = os.linesep.join(lMapping.splitlines())