计算一个单词中不同字符的数量

Question

I am trying to think of a program to count the number of different characters in a word in Python.

For example:

• Given the input:

   ('Banana')

• Expected output:

   3

How can I use a while or for loop to do this?

Thanks

Answer 1

A loop for this is not required. You can find the unique characters in a string using set

len(set('Banana'))

This will output 3 . If you want to see what characters are unique, remove the len wrapper:

set('Banana')

Outputs:

set(['a', 'B', 'n'])

---

Note: B and b are unique. If you have a word like Baby you'll get this:

set(['a', 'y', 'B', 'b'])

To prevent this, convert your string to either all caps or all lower case:

set('Baby'.lower())

Outputs:

set(['a', 'y', 'b'])

Answer 2

>>> len(set('Banana'))
3

Answer 3

Note: For future readers, this solution is only accepted because the OP was restricted to using loops. @Andy's solution provides a much better alternative using Python'sset() function.

Using a for loop:

word='Banana'

L=[]                           #create an empty list
for letter in word:
    if letter not in L:
        L.append(letter)       #append unique chars to list

print len(L)                   #count the chars in list