TypeError: 'int' object does not support item assignment

Question

p=range(0,1200,10)
lenp=len(p)
rp=1.331
po=1000
T=280
Temp=(lenp)

for i in p:
    Temp[i]=T*(p[i]/po)**rp
print T

Im getting this error and don't know how to fix it...

Temp[i]=T*(p[i]/po)**rp

TypeError: 'int' object does not support item assignment

Answer 1

You are presumably trying to build a list of length lenp here. You'd need to create a list by multiplication here:

Temp = [None] * lenp

but you'd be better off building the list by appending to it:

Temp = []
for i in p:
    Temp.append(T * (i / po) ** rp)

where you don't use p[i] but i directly ; Python for loops are for each loops really.

Your range() produces values in the series [0, 10, 20, ... 1200) and the for loop assigns each of those values to i per iteration. If you use i to index into p again you'd run into problems; p[0] would still be 0 , but p[10] would then be 100 , p[20] is 200 , etc. until p[120] throws an IndexError because there are only 119 different values in that range.

You can collapse the for loop appending to Temp into a list comprehension to build the list in one go:

rp=1.331
po=1000
T=280

Temp = [T * (i / po) ** rp for i in range(0, 1200, 10)]

Answer 2

There are a couple of issues in your code.

The most immediate one is that your Temp value is not a sequence that you can assign things to, just an integer (the parentheses don't do anything). While you could make it into a tuple by adding a comma, that still won't let you assign values into Temp after it has been created (tuples are immutable). Instead, you probably want a list.

However, there's another issue with your loop. A for loop like for value in sequence assigns values from the sequence to the variable value . It doesn't assign indexes! If you need indexes, you can either use enumerate or use a different looping construct, such as a list comprehension.

Here's a minimally changed version of your code that first creates a list of lenp zeros, then replaces their values with the computed ones:

p=range(0,1200,10)
lenp=len(p)
rp=1.331
po=1000
T=280
Temp=[0]*lenp

for i, p_value in enumerate(p):
    Temp[i]=T*(p_value/po)**rp
print T

Here's a more pythonic version that uses a list comprehension instead of an ordinary loop:

rp=1.331
po=1000
T=280
Temp = [T*(p_value/po)**rp for p_value in range(0,1200,10)]

Answer 3

Your Temp is not a tuple, it's just an integer in parenthesis. You can fix this with a simple , . Consider the following:

>>> x = (42)  # not a tuple
>>> x[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object has no attribute '__getitem__'
>>> 
>>> x = (42,)  # tuple
>>> x[0]
42

However , tuples are immutable, and you cannot perform such an assignment:

>>> x[0] = 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

You can fix this issue by using a list instead.

Answer 4

The mistake is that when we assign a (number) to x, this is what is actually happening,

>>> x = (50)
>>> x
50

So if you want to create an empty list , you can do it this way

rows = 5
cols = 3
matrix = [[0 for c in range(cols)] for r in range(rows)]

Its gonna create something like this one,

>>> matrix
[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]]