从另一个脚本运行脚本时出现 NameError

Question

我正在尝试从给定目录（包括子目录）运行脚本并检查它们的执行时间。 当涉及到声明很少函数的脚本时，除了主函数之外，我为每个函数得到 NameError: name %method_name% is not defined。

这是我运行脚本的方式：

def run_scripts(path):
    subdirs = os.listdir(path) 
    for subdir in subdirs:
        print('folder ' + subdir)
        files = os.listdir(path+'/'+subdir) 
        for file in files:
            print(os.path.dirname(file))
            if file.endswith('py'): 
                print('script \"' + os.path.basename(file) + '\"')
                print("output ", end='')
                start_time = time.time()
                exec(open(path+'/'+subdir+'/'+file, encoding='utf-8').read())
                print("time: %s seconds" % (time.time() - start_time))

这是引发 NameError 的可执行脚本的一部分：

filename = 'wiki.txt'

def letters_only(s):
    s = s.strip()
    for c in s:
        if not ((c >= 'a' and c <= 'z') or (c >= 'A' and c <= 'Z') or c == ' '):
            s = s.replace(c, '')
    return s 

def count_words(s):
    result = {}
    words = s.split()
    for w in words:
        if w in result.keys():
            result[w] += 1
        else:
            result[w] = 1
    return result

# other methods...

# main function
def wiki_function():
    f = open('wiki.txt', 'r', encoding='utf-8')
    data = f.readlines() 
    for line in data:
        print(line)
    non_empty = []
    for line in data:
        if (line != '') and (line != '\n'):
            non_empty.append(letters_only(line)) # NameError
    text = ' '.join(non_empty)
    word_freq = count_words(text) # NameError
    # ...

if __name__ == '__main__':
    wiki_function() 

我应该怎么做才能使功能正常工作？