Python: 'float' object is not subscriptable when iteration function

Question

I am teaching myself Python and am trying out a challenge I found to create a quote program for a gardener. I have almost all of it working and have added in iteration so that the user can make more than one quote without re-starting the program.

It produces the quote perfectly the first time but on the second run it presents this error:

Traceback (most recent call last):

  File "/Users/shaunrogers/Desktop/Plymstock Prep/GCSE CS/SOL/Controlled Assessment/Sample Papers Solutions/gardening Task 2.py", line 105, in <module>

    lawn = m2_items("lawn",0)
  File "/Users/shaunrogers/Desktop/Plymstock Prep/GCSE CS/SOL/Controlled Assessment/Sample Papers Solutions/gardening Task 2.py", line 23, in m2_items

    minutes = area*time[index]

TypeError: 'float' object is not subscriptable

I have the following code as a function that is producing the error:

def m2_items (item,index):

    global costs, time, LABOUR

    length = int(input("How long is the "+ item+"?\n"))

    width = int(input("How wide is the "+item+"?\n"))

    area = length*width

    cost_m2 = float(costs[index])

    total_cost = area*cost_m2

    minutes = area*time[index]

    hours = int(minutes/60)

    labour = LABOUR*hours

    labour_cost=round(labour,2)

    m2_details = [area, cost_m2, total_cost,hours, labour_cost]

    return m2_details

I have tried re-setting the local variables on the running of the function (but I didn't think this was needed as the variables should be removed from memory once the function has run).

I hope the question is clear and that I can get some insight. To re-iterate, what I want the program to do is allow me to call this function multiple times.

Isn't it clear that area*time returns float number and number is not a collection (list, dictionary, set, string etc. - for these types getting an element at [index] is a valid operation)? And nothing stops you to call this function multiple times. This is not the complete code. Show us how you are calling this function. — ElmoVanKielmo
– ElmoVanKielmo, Commented Jul 28, 2015 at 8:26
time is a float type object but you're attempting to access it like a dictionary or list. Should time have a different type? Or did you misunderstand the syntax when doing time[index]? — SuperBiasedMan
– SuperBiasedMan, Commented Jul 28, 2015 at 8:57

André Laszlo · Accepted Answer · 2015-07-28 08:58:04Z

1

You are using the global time variable, which is initially subscriptable (probably an array). As your program continues, some other part of your code will assign a new value to time, maybe accidentally because you wrote time = some_calculation() instead of time[i] = some_calculation(), or maybe you are using the name time somewhere else without realizing it's already in use.

Do a search for all the places where you use the name time and you will probably find your error.

This is a common problem with global variables. Sometimes something updates them from another part of the code, and the error will sneak up on you like this.

answered Jul 28, 2015 at 8:58

André Laszlo

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3 Comments

Shaun Rogers Over a year ago

Thank you Andre, That was exactly it. As soon as i read your answer it clicked an sorted my problem. Thank you for your help.

André Laszlo Over a year ago

So glad to hear you solved this! :) Learning Python is fun, but you get stuck sometimes. I hope you find StackOverflow a good place to learn. If you found this answer helpful you can mark it as accepted.

Shaun Rogers Over a year ago

Hi Andre, I have marked this and answered. Yours was by far the most helpful. I think I couldn't see the wood for the trees and within the first two sentences of your answer I knew exactly what I had done wrong. Thanks again

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