python_print函数的flush参数

今天发现了一个奇怪的现象，直接上代码

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1. import sys
   
2. from colorama import Fore, Back, Style
   
3. 
   
4. def print_example():
   
5.     print(Fore.RED+ "1. This is the first sentence")
   
6.      long_str=' Blowing in the wind'
   
7.     print(Fore.WHITE + '2. long_str =', end='')
   
8.     #print('2. long_str= ', end='')
   
9.     print( long_str,file=sys.stderr)
   
10.     print(Fore.CYAN + "3. Do they printed in right order")
    
11. 
    
12. print_example()
    
13. 
    
14. 打印出来的结果并不是我设想的顺序
    
15. 
    
16. 1. This is the first sentence
    
17.  Blowing in the wind
    
18. 2. long_str =3. Do they printed in right order

为什么stderr和stdout会打印到一起呢? 我的猜想也许跟stdout, stderr的缓冲机制有关后来发现python 3.3 后print可以加flush参数, 这样就能得到我想要的打印次序

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1. import sys
   
2.     from colorama import Fore, Back, Style
   
3.     def print_example():
   
4.         print(Fore.RED+ "1. This is the first sentence")
   
5.          long_str=' Blowing in the wind'
   
6.         print(Fore.WHITE + '2. long_str =', end='',flush=True)
   
7.         #print('2. long_str= ', end='')
   
8.         print( long_str,file=sys.stderr)
   
9.         print(Fore.CYAN + "3. Do they printed in right order")
   
10.     print_example()
    
11.     打印出来如下
    
12.     1. This is the first sentence
    
13.     2. long_str = Blowing in the wind
    
14.     3. Do they printed in right order

最后附上参考资料如何使用python打印彩色

Print Colors in Python terminal