如何修复TypeError：int与NoneType不支持减法运算的问题

错误原因 #

你遇到的TypeError: unsupported operand type(s) for -: 'int' and 'NoneType'，是因为计算会话时长时仅判断了end_time不为空，但未检查start_time是否存在。当某个会话只有END记录、没有对应的START记录时，start_time仍为None，此时用整数类型的end_time减去None就会触发该错误。

修复代码 #

修改计算duration的条件判断，同时检查start_time和end_time是否都不为None，关键代码调整如下：

# 替换原有的duration计算行
session['duration'] = session['end_time'] - session['start_time'] if (session['end_time'] is not None and session['start_time'] is not None) else None

同时优化时间格式化输出的容错性，完整修复后的脚本如下：

import json
from datetime import datetime

def parse_output_file(file_path):
    with open(file_path, 'r') as file:
        data = json.load(file)
    
    sessions = {}
    
    for record in data:
        session_id = record['id']
        session_type = record['type']
        timestamp = int(record['timestamp'])
        comments = record.get('comments', '')
        
        if session_id not in sessions:
            sessions[session_id] = {'id': session_id, 'start_time': None, 'end_time': None, 'duration': None, 'late_return': False, 'damaged': False, 'comments': ''}
        
        if session_type == 'START':
            sessions[session_id]['start_time'] = timestamp
        elif session_type == 'END':
            sessions[session_id]['end_time'] = timestamp
            sessions[session_id]['damaged'] = bool(comments)
            sessions[session_id]['comments'] = comments
    
    for session in sessions.values():
        # 避免start_time/end_time为None时格式化报错
        start_time = datetime.fromtimestamp(session['start_time']).strftime('%Y-%m-%d %H:%M:%S') if session['start_time'] is not None else "未记录"
        end_time = datetime.fromtimestamp(session['end_time']).strftime('%Y-%m-%d %H:%M:%S') if session['end_time'] is not None else "未记录"
        
        # 同时校验开始和结束时间是否存在
        session['duration'] = session['end_time'] - session['start_time'] if (session['end_time'] is not None and session['start_time'] is not None) else None
        late_return = session['duration'] > 24 * 3600 if session['duration'] is not None else False
        
        session['late_return'] = late_return
        
        print(f"Session ID: {session['id']}")
        print(f"Start Time: {start_time}")
        print(f"End Time: {end_time}")
        print(f"Duration: {session['duration']} seconds" if session['duration'] is not None else "Duration: 无效（缺少开始/结束时间）")
        print(f"Late Return: {late_return}")
        print(f"Damaged: {session['damaged']}")
        print(f"Comments: {session['comments']}")
        print()

file_path = r'output.json'
parse_output_file(file_path)

额外优化建议 #

• 处理原始数据时，可对每个会话的START/END记录做校验，比如发现同一个会话存在多条START或END记录时，输出警告或做合并处理。
• 对缺少start_time或end_time的会话，输出时明确标记为无效，方便排查数据问题。

内容的提问来源于stack exchange，提问作者David Oh