AttributeError: 'module' object has no attribute 'maketrans'
网上搜了好久，还是没找到原因。后来仔细阅读了一段文档：
Actually, modules are searched in the list of directories given by the variable sys.path which is initialized from the directory containing the input script (or the current directory), PYTHONPATH and the installation- dependent default. This allows Python programs that know what they’re doing to modify or replace the module search path. Note that because the directory containing the script being run is on the search path, it is important that the script not have the same name as a standard module, or Python will attempt to load the script as a module when that module is imported.
一想可能是跟python所import的库重名了。再看看文件名，也没有错。后来列出了文件夹下所有文件的名字，终于发现有个文件名叫string.py,在追踪下上面这段程序错误，一下可能就是这个文件出了问题，导致python引用错误。把该文件名字改完，程序运行正常了。
真巧~~~