如何解决这个TypeError：字符串索引必须是整数？

Question

I'm new to python and may not be very familiar with the detailed syntax rules.

Can i know how this error can be solved? It points to line 6,7,8 and i'm not sure what went wrong. Thanks!

def calculate_average_expenditure(a):
    totalincome = 0
    totalsavings = 0
    count = 0
    for item in a:
        if (item['AGE2011'] >= 20 and item['AGE2011'] <= 30):
            totalincome += item['INC2011']
            totalsavings += item['SAV2011']
            count += 1

    totalexpenditure = totalincome-totalsavings
    return totalexpenditure/count

EDIT: Thanks, i got it working by tweaking how the method is called.

a={ 'uen': 's1234567h', 'AGE2011':21, 'INC2011':100, 'SAV2011':80}
b={ 'uen': 's1234567h', 'AGE2011':28, 'INC2011':300, 'SAV2011':100}
x=[a,b]
calculate_average_expenditure(x)

Answer 1

I guess the parameter a is bound to a list of strings. Can you show how you call calculate_average_expenditure(...) and and what ... contains?