目标: 任务是写一个程序,它将一个字符串作为输入,并找到字符串中最频繁的字母,只有字母. 然后该程序应该打印最频繁的字母,然后在字符串中出现的次数. 字符串总是有一个最频繁的字母. 它是无病例的,所以'A'和'a'是相同的. 输入: str : 字符串,只包含必须忽略的字母和空格. 输出: 字符串中最频繁的字母r,其次是它在字符串中出现的次数. 它必须分开空间,并且字符被降低. 字符串的字母是字符串的最频繁的字母r. 字符串的最频繁的字母r是字符串的最频繁的字母r. 字符串的最频繁的字母r是字符串的最频繁的字母r. 字符串的最频繁的字母r是字符串的最频繁的字母r.
Here's one possible solution in Python:

```
def find_most_frequent_letter(s):
    # Create a dictionary to count the frequency of each letter
    freq = {}
    for c in s.lower():
        if c.isalpha():
            freq[c] = freq.get(c, 0) + 1
    # Find the most frequent letter and its frequency
    max_letter, max_count = None, 0
    for letter, count in freq.items():
        if count > max_count:
            max_letter, max_count = letter, count
    # Return the result as a lowercase string
    return max_letter.lower() + " " + str(max_count)

# Example usage:
s = "Hello, World!"
result = find_most_frequent_letter(s)
print(result)  # Output: "l 3"
```

The `find_most_frequent_letter` function first creates a dictionary `freq` to count the frequency of each letter in the input string. It ignores spaces and converts all letters to lowercase using the `isalpha()` and `lower()` methods.

Then, it loops through the dictionary to find the most frequent letter and its frequency. It initializes `max_letter` and `max_count` to `None` and `0`, respectively, and updates them whenever a letter with a higher frequency is found.

Finally, it returns the most frequent letter and its frequency as a lowercase string separated by a space. The example usage shows how to call the function with an example input string and print the result.