您如何在Python中编写一个函数，该函数需要一个字符串并返回一个新字符串，该字符串是原始字符串，并且重复了所有字符？

Question

I am trying to write a function that returns a string that is the inputted string with double characters. For example, if the input was 'hello', then the function should return 'hheelllloo'. I have been trying but I can't seem to find a way to write the function. Any help would be greatly appreciated--Thanks.

Answer 1

With a simple generator:

>>> s = 'hello'
>>> ''.join(c * 2 for c in s)
'hheelllloo'

Answer 2

def repeatChars(text, numOfRepeat):
    ans = ''
    for c in text:
        ans += c * numOfRepeat
    return ans

To use:
repeatChars('hello', 2)
output: 'hheelllloo'

Since strings are immutable, it's not a good idea to concatenate them together as seen in the repeatChars method. It's okay if the text you're manipulating has short length like 'hello' but if you're passing 'superfragilisticexpialidocious' (or longer strings)... You get the point. So as an alternative, I've merged my previous code with @Roman Bodnarchuk's code.

Alternate method:

def repeatChars(text, numOfRepeat):
    return ''.join([c * numOfRepeat for c in text])

Why? Read this: Efficient String Concatenation in Python

Answer 3

s = 'hello'
''.join(c+c for c in s)

# returns 'hheelllloo'

Answer 4

>>> s = "hello"
>>> "".join(map(str.__add__, s, s))
'hheelllloo'

Answer 5

def doublechar(s):
    if s:
        return s[0] + s[0] + doublechar(s[1:])
    else:
        return ""