start.py

# import sys,os
# #os.path.abspath(__file__) # 取当前路径的绝对路径
#
#
# print(os.path.abspath(__file__))
# # /Users/sg/PycharmProjects/py-study/ATM/bin/start.py
#
# print(os.path.dirname(os.path.abspath(__file__)))
# # /Users/sg/PycharmProjects/py-study/ATM/bin

# print(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
# # /Users/sg/PycharmProjects/py-study/ATM
# 定义ATM的路径作为起始路径，方便各个模块之间的变量导入


import os,sys
BASE_DIR=os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
sys.path.append(BASE_DIR)

from core import src
if __name__ == '__main__':
    src.run()

setting.py

# 定义各个模块的路径
import os
BASE_DIR=os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
# 以上路径为/Users/sg/PycharmProjects/py-study/ATM

LOG_PATH=os.path.join(BASE_DIR,'log','access.log')
DB_PATH=os.path.join(BASE_DIR,'db','user')

或
DB_PATH=r'%s/db/db.txt' %BASE_DIR
LOG_PATH=r'%s/log/user.log' %BASE_DIR


# print(LOG_PATH)
# # /Users/sg/PycharmProjects/py-study/ATM/log/access.log
#
# print(DB_PATH)
# # /Users/sg/PycharmProjects/py-study/ATM/db/user

src.py

from lib import common
def shop():
    print('购物。。。')

def check_balance():
    print('查看余额。。。')

def transfer_accounts():               
    print('转账。。。')
    log_msg='转账了一个亿'                  #定义了日志输出
    common.logger(log_msg)



def  run():
    msg='''
    1 购物
    2 查看余额
    3 转账
    '''

    while True:
        print(msg)
        choice=input('>>:').strip()
        if not choice:continue
        if choice == '1':
            shop()
        elif choice == '2':
            check_balance()
        elif choice == '3':
            transfer_accounts()

另一参考版本---------------------------------
from conf import  setting
# from lib import common
# 
# def login():
#     count=0
#     while True:
#         name=input('name:').strip()
#         password=input('password:').strip()
#         res=common.select(name)
#         if name==res[0] and password==res[1]:
#             print('%s 登录成功' %name)
#         else:
#             print('用户名或密码输入错误')
#             count+=1
#         if count == 3:
#             print('输入错误次数过多！')
#             break
# 
# 
# 
# def register():
#     name = input('name:').strip()
#     password = input('password:').strip()
#     with open(setting.DB_PATH,'a',encoding='utf-8') as f:
#         f.write('%s:%s\n' %(name,password))
#         common.logger('%s 注册成功\n' %name)
#         print('注册成功')
# 
# 
# def shopping():
#     pass
# 
# def pay():
#     pass
# 
# def transfer():
#     pass
# 
# func_dir={
#     '1':login,
#     '2':register,
#     '3':shopping,
#     '4':pay,
#     '5':transfer
# }
# 
# 
# def run():
#     while True:
#         print('''
#         1 登录
#         2 注册
#         3 购物
#         4 付款
#         5 转账
#         6 退出
#         ''')
#         choice=input('输入编号：').strip()
#         if choice == '6':break
#         if choice not in func_dir:
#             print('非法输入')
#             continue
#         func_dir[choice]()

common.py

# 定义日志输出文件路径
from conf import settings

def logger(msg):
    with open(settings.LOG_PATH,'a',encoding='utf-8') as f:
        f.write('%s\n' %msg)

参考另一版本------------
# import time
# from conf import  setting
# 
# 
# def logger(msg):
#     current_time=time.strftime('%Y-%m-%d %X')
#     with open(setting.LOG_PATH,'a',encoding='utf-8') as f:
#         f.write('%s %s' %(current_time,msg))
# 
# def select(name):
#     with open(setting.DB_PATH, 'r', encoding='utf-8') as f:
#         for line in f:
#             info=line.strip('\n').split(':')
#             return info

执行start.py验证

/usr/local/bin/python3 /Users/shiheng/PycharmProjects/py-study/ATM/bin/start.py

    1 购物
    2 查看余额
    3 转账
    
>>:3
转账。。。

    1 购物
    2 查看余额
    3 转账
    





查看access.log内容为：
转账了一个亿