python：遍历文件夹下所有/特定的文件

引入

在实际项目中，常需要批量处理某些文件夹下的子文件夹/文件。因此就需要遍历文件夹下所有的文件。
若只想读取特定的文件，就是在遍历过程中加一个条件判断即可，比如限定只访问特定后缀名的文件。
在python中，可通过os模块的os.walk()轻松实现对文件夹的遍历。

os.walk()

接口的基本使用：

• 传入参数top，即需要遍历的根文件夹
• 返回结果是一个生成器，可通过for循环去迭代其中的元素，就是一个从上至下的目录树。

Signature: os.walk(top, topdown=True, onerror=None, followlinks=False)
Docstring:
Directory tree generator.

For each directory in the directory tree rooted at top (including top
itself, but excluding '.' and '..'), yields a 3-tuple

    dirpath, dirnames, filenames

dirpath is a string, the path to the directory.  dirnames is a list of
the names of the subdirectories in dirpath (excluding '.' and '..').
filenames is a list of the names of the non-directory files in dirpath.
Note that the names in the lists are just names, with no path components.
To get a full path (which begins with top) to a file or directory in
dirpath, do os.path.join(dirpath, name).

实例1

功能：获取某一文件夹下的所有文件名

import os
def get_all_file(dir_name):
    fullname_list, filename_list = [], []
    for root, dirs, files in os.walk(dir_name):
        for filename in files:
            # 文件名列表，包含完整路径
            fullname_list.append(os.path.join(root, filename))
            # # 文件名列表，只包含文件名
            filename_list.append(filename)
    return fullname_list, filename_list

实例2

功能：打印某一文件夹下的所有文件/子文件夹信息

import os
from os.path import join, getsize

dir_name = 'C:\Users\Public'
for root, dirs, files in os.walk(dir_name):
    # print(root, dirs, files)
    info = f'''
        {root} contains {len(files)} non-directory files, they are {files}
               contains {len(dirs)} sub-directories, they are {dirs}
    '''
    print(info)