Python解析YAML遇空port键触发KeyError，需优化处理方案

我有大量结构相似但数据不同的YAML文件，需要从中提取指定数据写入单个CSV文件的对应列。但解析时遇到空的port键会触发「KeyError: 'port'」报错，示例YAML中第二个base块的port值为空，需求是遇到空键时不写入任何内容。

YAML文件示例 #

base:
   server: 10.100.80.47
   port: 3306
   namePrefix: well
   user: user1
   password: kjj&%$

base:
   server: 10.100.80.48
   port: 
   namePrefix: done
   user: user2
   password: fhfh#$%

当前Python代码 #

from asyncio.windows_events import NULL
from queue import Empty
import yaml
import csv
import glob


yaml_file_names = glob.glob('./*.yaml')

rows_to_write = []

for i, each_yaml_file in enumerate(yaml_file_names):
 print("Processing file {} of {} file name: {}".format(
  i+1, len(yaml_file_names),each_yaml_file))

 with open(each_yaml_file) as file: 
  data = yaml.safe_load(file)


for v in data:
 if "port" in v == "": 
 data['base']['port'] = ""  



rows_to_write.append([data['base']['server'],data['base']['port'],data['server']['host'],data['server']['contex']])


with open('output_csv_file.csv', 'w', newline='') as out:
 csv_writer = csv.writer(out)
 csv_writer.writerow(["server","port","hostname", "contextPath"])
 csv_writer.writerows(rows_to_write)
 print("Output file output_csv_file.csv created")

问题分析与修正方案 #

你的代码存在多处逻辑错误，导致无法正确处理多文件和空port的情况，以下是修正后的代码及关键说明：

修正后的代码 #

import yaml
import csv
import glob

yaml_file_names = glob.glob('./*.yaml')
rows_to_write = []

for i, each_yaml_file in enumerate(yaml_file_names):
    print(f"Processing file {i+1} of {len(yaml_file_names)} file name: {each_yaml_file}")
    with open(each_yaml_file) as file:
        data = yaml.safe_load(file)
    
    # 用get方法安全获取值，避免KeyError，空值时返回空字符串
    server = data.get('base', {}).get('server', '')
    port = data.get('base', {}).get('port', '')
    # 注意：原代码中的data['server']在示例YAML中不存在，这里用get方法容错，同时修正contex为context
    hostname = data.get('server', {}).get('host', '')
    context_path = data.get('server', {}).get('context', '')
    
    rows_to_write.append([server, port, hostname, context_path])

with open('output_csv_file.csv', 'w', newline='', encoding='utf-8') as out:
    csv_writer = csv.writer(out)
    csv_writer.writerow(["server", "port", "hostname", "contextPath"])
    csv_writer.writerows(rows_to_write)
print("Output file output_csv_file.csv created")

关键修正点 #

• 多文件处理逻辑：将数据提取和添加到rows_to_write的代码放到YAML文件循环内部，确保每个文件的数据都被处理，而不是只保留最后一个文件的内容
• 安全获取字典值：使用字典的get()方法，格式为dict.get(key, 默认值)，即使键不存在或者值为空，也会返回指定的默认值（这里用空字符串），彻底避免KeyError
• 键名错误修正：原代码中data['server']['contex']存在拼写错误，修正为context，同时用get()方法容错，避免因YAML中无server节点报错
• 代码简化：删除无用的导入（NULL、Empty），使用f-string简化打印语句，添加编码参数确保CSV文件兼容性

内容的提问来源于stack exchange，提问作者Paulo