如何在python中扭轉字符串？

最常用且最Pythonic的字符串反轉方法是使用切片。 1. 使用切片[::-1] 是最推薦的方法，因為它簡潔、高效且易讀；2. 使用''.join(reversed(text)) 更加直觀，適合初學者理解；3. 使用循環通過逐個前置字符實現，但因字符串不可變性導致性能較差，不推薦用於大字符串；4. 使用遞歸方法適合教學演示，但存在調用開銷和遞歸深度限制，不適合長字符串。實際應用中應優先選擇切片方法，即text[::-1]，以獲得最佳性能和可讀性。

Reversing a string in Python is simple thanks to built-in features. Here are the most common and effective ways:

1. Using slicing (most common and Pythonic)

The easiest way to reverse a string is using Python's slicing syntax:

 text = "hello"
reversed_text = text[::-1]
print(reversed_text) # Output: "olleh"

• The [::-1] means: slice the string from start to end with step -1, which reverses it.
• This method is fast, readable, and widely used.

2. Using the reversed() function with join()

You can use the built-in reversed() function, which returns an iterator, and combine it with ''.join() :

 text = "hello"
reversed_text = ''.join(reversed(text))
print(reversed_text) # Output: "olleh"

• This is more explicit and readable for beginners.
• Slightly more verbose than slicing, but just as effective.

3. Using a loop (manual approach)

If you want to reverse a string manually (eg, for learning or interviews), you can use a loop:

 text = "hello"
reversed_text = ""

for char in text:
    reversed_text = char reversed_text # prepend each character

print(reversed_text) # Output: "olleh"

• This works, but it's less efficient because strings are immutable in Python — each char reversed_text creates a new string.
• Not recommended for large strings.

4. Using recursion (for educational purposes)

Another way to reverse a string is with recursion:

 def reverse_string(s):
    if len(s) <= 1:
        return s
    return s[-1] reverse_string(s[:-1])

text = "hello"
print(reverse_string(text)) # Output: "olleh"

• This is elegant but inefficient for long strings due to function call overhead and recursion limits.
• Best used to demonstrate algorithmic thinking.

Which method should you use?

• ✅ Use slicing ( [::-1] ) in most real-world cases — it's fast and clean.
• ✅ Use ''.join(reversed(text)) if you prefer more readable, self-explanatory code.
• ? Avoid loops or recursion for simple tasks unless you're learning or under specific constraints.

Basically, text[::-1] is the go-to solution.

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