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《effective python》- python默认参数

news 2026/3/26 20:25:25

《effective python》- python默认参数

 1 import json
 2 import time
 3 from datetime import datetime
 4 
 5 
 6 def print_log(msg: str, when=None):
 7     when = datetime.now() if when is None else when
 8     print(f'time:{when} print msg:{msg}')
 9 
10 
11 print_log('msg')
12 time.sleep(5)
13 print_log('msg')
14 
15 
16 def decode(data: str, default={}):
17     try:
18         return json.loads(data)
19     except ValueError:
20         return default
21 
22 
23 foo = decode('bad data')
24 foo['stuff'] = 5
25 bar = decode('also bad')
26 bar['meep'] = 1
27 print(f'foo:{foo}')
28 print(f'bar:{bar}')
29 
30 
31 def decode_v2(data: str, default=None):
32     default = {} if default is None else default
33     try:
34         return json.loads(data)
35     except ValueError:
36         return default
37 
38 foo = decode_v2('bad data')
39 foo['stuff'] = 5
40 bar = decode_v2('also bad')
41 bar['meep'] = 1
42 print(f'foo:{foo}')
43 print(f'bar:{bar}')