从字符串Python中删除字符

Question

I'm trying to write a function that gets rid of the vowels in a given string, but it seems to not behave the way it should do...

def anti_vowel(text):
    for c in text:
        if c in "aeiouAEIOU":
            no_vowel = text.replace(c, '')
    return no_vowel
print(anti_vowel('Hello World')

so instead of printing

Hll Wrld

It prints

Hell Wrld  

Thanks (in advance) for helping

Answer 1

The problem is that no_vowel only has the value of the last time that text.replace(c, '') was executed. Another issue is that no_vowel only gets a value when there is actually a vowel to remove; the code would fail on anti_vowel('vwllss') . Furthermore, you don't have to check whether a character is contained in the text before calling str.replace() .

This should work:

def anti_vowel(text):
    for vowel in "aeiouAEIOU":
        text = text.replace(vowel, '')
    return text
print(anti_vowel('Hello World'))

As others indicated, another approach would be to write code in a different way:

def anti_vowel(text):
    ''.join(c for c in text if c not in 'aeiouAEIOU')

Please do use a generator expression in ''.join() and not a list comprehension; such a list comprehension would allocate memory unnecessarily.

Answer 2

You can use string.translate() for this. For example:

def anti_vowel(text):
  return text.translate(None, "aeiouAEIOU")

print(anti_vowel("hello world"))

With Python 3 the delete argument is gone, but you can still do it by mapping a character to None .

def anti_vowel_py3(text):
   return text.translate({ord(i): None for i in "aeiouAEIOU"})

print(anti_vowel_py3("hello world"))

Answer 3

Your code doesnt work because every iteration you assign no_vowel with the text all over again and you iterate the text's letters what you shouldnt because replace already does it. You should write it like that:

def anti_vowel(text):
    no_vowel = text
    for c in 'aeiouAEIOU':
        no_vowel = no_vowel.replace(c, '')

    return no_vowel

Or, you could use a list comprehension. More Pythonic and faster to run:

def anti_vowel(text):
    return ''.join([c for c in text if c not in 'aeiouAEIOU])

Answer 4

In every iteration of the loop, text is "Hello World", and the last vowel of text is "o", so at the end of the loop, no_vowel is "Hell Wrld".

In python2.7, use method translate instead. Here is the official document:

translate(...)

  S.translate(table [,deletechars]) -> string Return a copy of the string S, where all characters occurring in the optional argument deletechars are removed, and the remaining characters have been mapped through the given translation table, which must be a string of length 256 or None. If the table argument is None, no translation is applied and the operation simply removes the characters in deletechars. 

"Hello World".translate(None, "aeiouAEIOU") gives the correct result "Hll Wrld"

Also, re.sub('[aeiouAEIOU]', "", "Hello World") works for both python2.7 and python3