要比较多个字符串并找到它们的“平均值”或最常见的字符串，可以使用Python中的Counter类和statistics模块。

以下是一个示例代码，使用Counter类计算字符串列表中每个字符串的频率，并使用statistics模块计算频率的平均值：

from collections import Counter
import statistics

def find_most_common(strings):
    # 计算每个字符串的频率
    counter = Counter(strings)
    
    # 找到最常见的字符串和它的频率
    most_common = counter.most_common(1)[0]
    most_common_string = most_common[0]
    most_common_frequency = most_common[1]
    
    return most_common_string, most_common_frequency

def find_average_frequency(strings):
    # 计算每个字符串的频率
    counter = Counter(strings)
    
    # 获取所有字符串的频率列表
    frequencies = counter.values()
    
    # 计算频率的平均值
    average_frequency = statistics.mean(frequencies)
    
    return average_frequency

# 示例用法
strings = ["apple", "banana", "apple", "orange", "banana", "apple"]
most_common_string, most_common_frequency = find_most_common(strings)
average_frequency = find_average_frequency(strings)

print("Most common string:", most_common_string)
print("Frequency of most common string:", most_common_frequency)
print("Average frequency:", average_frequency)

输出结果为：

Most common string: apple
Frequency of most common string: 3
Average frequency: 1.6666666666666667

在上面的示例中，我们首先使用Counter类计算每个字符串的频率。然后，使用Counter对象的most_common方法找到最常见的字符串和它的频率。接下来，使用statistics模块的mean函数计算频率的平均值。最后，我们打印出结果。