遍历列，不可迭代

Question

What causes the code below to give the following error on line 8:

Type error: 'Float' object is not iterable

for column in usable_columns:
    cardinality = len(np.unique(x_train[column]))
    if cardinality == 1:
        x_train.drop(column, axis=1) # Column with only one 
        # value is useless so we drop it
        x_test.drop(column, axis=1)
    if cardinality > 2: # Column is categorical
        mapper = lambda x: sum([ord(digit) for digit in x])
        x_train[column] = x_train[column].apply(mapper)
        x_test[column] = x_test[column].apply(mapper)
   x_train.head()

Answer 1

A for loop can only function if the number of times it iterates is a whole number. whatever the variable column is, its being stored as a float not an integer (ie 3.0 instead of 3) Assuming that column is a whole number, either use column=int(column) before the for loop or type for int(column) in usable_columns as your for loop