类型错误：列表索引必须是整数，而不是 str（在我的代码中，Python）

Question

vvod = input('Input: ')
vvod_a = []
for i in vvod:
    vvod_a.append(i)
print (vvod_a)
for i in vvod_a:
    if i == 'a' or 'b' or 'c':
        vvod_a[i] = 'bg'

print (vvod_a)

Traceback (most recent call last):
['f', 'e', 'f', 's', 'f', 'f', 'a', 'a', 'f', 'a', 'e']
  File "/home/n4/Рабочий Влад/PYTHON/coding", line 8, in <module>
    vvod_a[i] = 'bg'
TypeError: list indices must be integers, not str

Help me please,if i in list 'a' or 'b' or 'c', then i will be 'bg'.

Answer 1

First, you ask for input() , producing a string. Then you do for i in vvod: vvod_a.append(i) to turn this string into a list of 1-character strings (for future reference, you can do this with vvod_a = list(vvod) ). This produced the list : ['f', 'e', 'f', 's', 'f', 'f', 'a', 'a', 'f', 'a', 'e'] . Then you attempt to modify some of these with if i == 'a' or 'b' or 'c': , but this is equivalent to if (i=='a') or ('b') or ('c') , and since a non-empty string is truthy, you then get a condition that's always true.

Then we get to the actual problem: vvod_a[i] = 'bg' . You are iterating over the actual elements in the list , not its indices. i is a string, not an integer that could be used for list indexing.

I recommend the following minimal changes:

vvod = input('Input: ')
vvod_a = []
for i in vvod:
    vvod_a.append(i)

print (vvod_a)
for i in range(len(vvod_a)):
    if vvod_a[i] in 'abc':
        vvod_a[i] = 'bg'

print (vvod_a)

If you want to tighten up your code, you could use a dictionary combined with the get method in a list comprehension:

vvod = input('Input: ')
change_map = {'a':'bg', 'b':'bg', 'c':'bg'}
vvod_a = [change_map.get(item, item) for item in vvod]
print(vvod_a)

Answer 2

As TigerhawkT3 has pointed out, the two main problems in your code are that in the for loop you use the actual elements of the list as index ( vvod_a[i] in line 8), and that the if condition in line 7 fails to compare the expression in the left-hand side of the condition with each of the elements in the right-hand side. As an alternative solution, I would suggest the use of enumerate():

vvod = input('Input: ')
vvod_a = []
for i in vvod:
     vvod_a.append(i)
print (vvod_a)
for index, i in enumerate(vvod_a):
    if i == 'a' or i == 'b' or i == 'c':
        print(i)
        vvod_a[index] = 'bg'
        print(vvod_a)

print (vvod_a)