How do i debug my cgi script with mysql database in python. I am new to how to debugg
Question
My code is showing some error when runing on server. i checked the server error log and still not knowing what the exact it mean to say. It says premature end of script. Now I want to debug my code to check each and every line of code to what does it do ? How am i supose to debugg my code. I am really new to this.
#!/usr/bin/python
import cgitb
import MySQLdb
import cgi
cgitb.enable()
form = cgi.FieldStorage()
f_name = form.getvalue('firstname', '')
l_name = form.getvalue('lastname', '')
age = form.getvalue('age', 0)
gender = form.getvalue('gender', '')
db = MySQLdb.connect("localhost", "root", "gaurav", "Info")
cursor = db.cursor()
sql = "INSERT INTO PERSON (F_Name, L_Name, Age, Gender) VALUES ('%s',' %s',' %d',' %s')" % (f_name, l_name, age, gender)
try:
cursor.execute(sql)
#print "Hello !!"
#print "no of rows inserted: %d " % cursor.rowcount
db.commit()
except:
db.rollback()
db.close()
print "Content-type:text/html"
print "<html>"
print "<h1>DATABASE</h1>"
print "</html>"
2 answers
solution1
2 ACCPTED 2013-11-12 06:21:54
The problem is that in HTTP, the headers have to end with a blank line. So, instead of sending one header line and a 3-line body, you're sending four header lines, all but one of which are nonsense, and then exiting without ever finishing the headers.
So, the server complains that the script exited without finished writing the response.
Try this:
print "Content-type:text/html"
print
print "<html>"
print "<h1>DATABASE</h1>"
print "</html>"
If you want to log every line of code, as you said in the comments, there are two ways to do it.
The quick&dirty way is to just open a file and write into it. For example:
#!/usr/bin/python
import cgitb
import MySQLdb
import cgi
with open('/tmp/logfile.log', 'wb') as logfile:
logfile.write('About to enable cgitb\n')
cgitb.enable()
logfile.write('About to create FieldStorage\n')
form = cgi.FieldStorage()
logfile.write('About to get firstname\n')
f_name = form.getvalue('firstname', '')
logfile.write('Firstname is {}. About to get lastname\n'.format(firstname))
l_name = form.getvalue('lastname', '')
logfile.write('Lastname is {}. About to get age\n'.format(lastname))
# and so on
A cleaner way is to use the logging module that comes with Python:
#!/usr/bin/python
import cgitb
import MySQLdb
import cgi
import logging
logging.info('About to enable cgitb')
cgitb.enable()
logging.info('About to create FieldStorage')
form = cgi.FieldStorage()
This is simpler (no need to add \\n onto the end, the logger can format strings for you so you don't have to do it manually with .format or % , etc.). And it's a lot more flexible (you can log different messages at different levels, you can configure where the logs go—eg, send them to your system log instead of a file in /tmp, etc.). And it's more robust (no need to worry about forgetting to close the file and losing the last log messages—note that in the non- logging example, I used a with statement to get the same effect, but that required indenting the whole program).
If you have time to work through the Logging Tutorial , you should do so.
Finally, if you're pretty sure some line is raising an exception, but you can't find the exception information anywhere in the server logs, here's how to log the exception:
import traceback
try:
the line that raises
except Exception:
traceback.print_exc(None, logfile)
raise
This captures the exception, prints out the exact same detailed traceback you would have gotten in a console interpreter session, but into the log file you opened earlier instead of to the console, then lets the exception propagate normally.
If you're using the logging module, you can use its own built-in exception logging, or if you want to customize things you can use sys.exc_info and traceback.format_exception to get a string (or series of strings) to log.
solution2
0 2013-11-12 09:14:11
By checking all the possibility of error i found a solution that sequence of import matters here
it should be like
import cgi
import MySQLdb
instead of
import MySQLdb
import cgi
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