python常见操作

1、数组for初始化

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1. Y=[ 2.5,3.51,4.45,5.52,6.47,7.51]
   
2. X = [x+1 for x in range(len(Y))]

2、字符串时间加减

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1. A="2007-07-06"
   
2. B="2007-07-26"
   
3. def getDay_num(start,end):
   
4.         x = datetime.datetime.strptime(end, '%Y-%m-%d')
   
5.         x2 = datetime.datetime.strptime(start, '%Y-%m-%d')
   
6.         v = x-x2
   
7.         return v.days
   
8. print getDay_num(A,B)

3、词典值为空判断
加上跟踪快速捕获错误

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1. dict = {}
   
2. dict["a"]="bbbbbbbbbb"
   
3. print dict['a']
   
4. if not dict.has_key('b'):
   
5.         print "addddddasdfdsaf"

4、python打印异常信息两种方式
1）、直接打印

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1. try:
   
2.  
   
3.     # your code
   
4.  except KeyboardInterrupt:
   
5.  
   
6.     print("quit")
   
7.  
   
8. except Exception as ex:
   
9.      print("出现如下异常%s"%ex)

2）、用traceback模块打印
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1. import traceback
   
2. try:
   
3.     2/0
   
4. except Exception as e:
   
5.     traceback.print_exc()

5、日志错误
加上跟踪快速捕获错误

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1. import logging
   
2. import logging.handlers
   
3. def LOG(str):
   
4. 
   
5.         logger = logging.getLogger("fetchlogs") # 获取名为tst的logger
   
6.         if not logger.handlers:
   
7.                 ISOTIMEFORMAT='%Y%m%d'
   
8.                 LOG_NAME= './fetchlogs/log_atr'
   
9.                 LOG_NAME = LOG_NAME+ time.strftime( ISOTIMEFORMAT, time.localtime())
   
10.                 LOG_NAME = LOG_NAME + ".txt"
    
11. 
    
12.                 handler = logging.handlers.RotatingFileHandler(LOG_NAME, maxBytes = 5*1024*1024, backupCount = 5)
    
13.                 fmt = '%(asctime)s - %(filename)s:%(lineno)s - %(name)s - %(message)s'
    
14. 
    
15.                 formatter = logging.Formatter(fmt) # 实例化formatter
    
16.                 handler.setFormatter(formatter) # 为handler添加formatter
    
17. 
    
18.                 logger.addHandler(handler) # 为logger添加handler
    
19.                 logger.setLevel(logging.DEBUG)
    
20. 
    
21. 
    
22.         logger.info(str)
    
23. 
    
24. def Log_exception(str):
    
25. 
    
26.         logger = logging.getLogger("fetchlogserr") # 获取名为tst的logger
    
27.         if not logger.handlers:
    
28.                 ISOTIMEFORMAT='%Y%m%d'
    
29.                 LOG_NAME= './fetchlogs/log_atr_err'
    
30.                 LOG_NAME = LOG_NAME+ time.strftime( ISOTIMEFORMAT, time.localtime())
    
31.                 LOG_NAME = LOG_NAME + ".txt"
    
32. 
    
33.                 handler = logging.handlers.RotatingFileHandler(LOG_NAME, maxBytes = 5*1024*1024, backupCount = 5)
    
34.                 fmt = '%(asctime)s - %(filename)s:%(lineno)s - %(name)s - %(message)s'
    
35. 
    
36.                 formatter = logging.Formatter(fmt) # 实例化formatter
    
37.                 handler.setFormatter(formatter) # 为handler添加formatter
    
38. 
    
39.                 logger.addHandler(handler) # 为logger添加handler
    
40.                 logger.setLevel(logging.DEBUG)
    
41. 
    
42. 
    
43.         logger.exception(str)

6、数组降维度

#reshape函数当参数只有一个-1时表示将数组降为一维

np.ravel 降为一维数组

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1. import numpy as np
   
2. t = ar(range(10),dtype = 'float32')
   
3. print t
   
4. 
   
5. t2= t.reshape((10,1))
   
6. print t2
   
7. t3=t2.reshape(-1)
   
8. print t3
   
9. 
   
10. print np.ravel(t2)