[Tutor] TypeError: object doesn't support item assignment [ Trying to learn how to enter value in array ]

[Brian van den Broek]

John Joseph said unto the world upon 02/01/06 02:48 AM:
 > Hi All
 >    I am trying to write a program in  which I enter
 > the no of students and then for the students I enter
 > the marks and later on Display the marks
 > The script which I wrote is  given below , when I run
 > the program I get error
 > “TypeError: object doesn't support item assignment “ ,
 > my aim in doing  this program is to learn how to enter
 > values in a array , please advice  how can I avoid
 > this error
 >            Guidance requested
 >                    Thanks
 >                      Joseph
 >
 > ##################################################################
 > # This program is to learn how u enter entry to the
 > array
 > # And how u print it ,
 >
 >
 > print " \nFirst Enter the No of Students ... "
 > print "\n Then No of marks "
 >
 > # defining empty array a
 > a = ()
 > # defining i
 > i = 0
 >
 > # n is the No of  students which I have to enter the
 > marks
 > n = int(raw_input("Enter the no: of students :  \n"))
 >
 >
 > # m is the Marks of the students which I have to enter
 > while i < n:
 >         m = int(raw_input("Enter the Marks for the
 > students :  \n"))
 >         a[i] = m
 >         print "Marks are ", m
 >         i = i+1
 >
 > #print "Array Marks ", a[i]

Hi John,

the whole traceback is helpful, as it (tries to) show the line that 
made Python choke:

Traceback (most recent call last):
   File "/home/tempos/foo.py", line 16, in -toplevel-
     a[i] = m
TypeError: object does not support item assignment

See how that shows us that it is the a[i] = m that is the problem?

See if this helps work it out:

 >>> a_tuple = ()
 >>> a_tuple[0] = "Won't work, as tuples are immutable"

Traceback (most recent call last):
   File "<pyshell#7>", line 1, in -toplevel-
     a_tuple[0] = "Won't work, as tuples are immutable"
TypeError: object does not support item assignment
 >>> a_list = []
 >>> a_list[0] = "Won't work, different reason"

Traceback (most recent call last):
   File "<pyshell#9>", line 1, in -toplevel-
     a_list[0] = "Won't work, different reason"
IndexError: list assignment index out of range
 >>> a_preloaded_list = [None]
 >>> a_preloaded_list[0] = "Will work, but not the best way generally"
 >>> a_preloaded_list
['Will work, but not the best way generally']
 >>>


It doesn't seem that you are aiming to correlate marks with students 
yet, but just want a list of marks. In that case:

 >>> marks = []  # 'a' is not a helpful name :-)
 >>> mark = raw_input("What mark?")
What mark?17
 >>> marks.append(mark)
 >>> mark = raw_input("What mark?")
What mark?42
 >>> marks.append(mark)
 >>> marks
['17', '42']
 >>>

HTH,

Brian vdB