How to double a char in a string?

问题

I am trying to write a function that takes two arguments, a string and a letter. The function should then double the number of letter in the string. For example:

double_letters("Happy", "p")
Happppy

what i have done so far;

def double_letter(strng, letter):
 new_word = ""
    for char in strng:
        if char == letter:
            pos = strng.index(char)
            new_word = letter+strng[pos:]

But this is giving me the output: pppy

how can i change the function to get the output: Happppy?

回答1:

Use string.replace

string = 'happy'
letter = 'p'
string = string.replace(letter, letter + letter)
print string

回答2:

You could use join and iterate through the characters in your string:

def double_letters(word, letter):
    return "".join(2*i if i == letter else i for i in word)

来源：https://stackoverflow.com/questions/22605967/how-to-double-a-char-in-a-string