用Python统计一个字符串中出现最多的字符和出现次数，

可以使用Python中的字典来实现该功能。具体实现步骤如下：

1. 定义一个空字典用于存储每个字符出现的次数。
2. 遍历字符串中的每个字符，如果该字符不在字典中，则将该字符添加到字典中，值为1；如果该字符已经在字典中，则将该字符对应的值加1。
3. 遍历字典，找到出现次数最多的字符和出现次数。

下面是具体的代码实现：

def find_most_frequent_char(s):
    char_dict = {}
    for char in s:
        if char not in char_dict:
            char_dict[char] = 1
        else:
            char_dict[char] += 1
    most_frequent_char = ''
    most_frequent_count = 0
    for char, count in char_dict.items():
        if count > most_frequent_count:
            most_frequent_char = char
            most_frequent_count = count
    return most_frequent_char, most_frequent_count

使用该函数可以找到字符串中出现次数最多的字符以及出现次数，例如：

s = 'hello world'
char, count = find_most_frequent_char(s)
print(f"The most frequent char is '{char}', which appears {count} times.")

输出结果为：

The most frequent char is 'l', which appears 3 times.