PySnooper：非常好用的python代码调试帮助工具！

       PySnooper是一个给平民用的调试器，因为它是完全免费的！使用pysnooper可以完整的输出函数每一行代码中的变量的值，供我们去观察。github网址：PySnooper - Never use print for debugging again

1.示例

       下面这个函数的功能是，通过返回一个位列表将数字转换为二进制。 然后通过添加@pysnooper.snoop() 装饰器来追踪它的每一行的变量的值：

import pysnooper @pysnooper.snoop() def number_to_bits(number): if number: bits = [] while number: number, remainder = divmod(number, 2) bits.insert(0, remainder) return bits else: return [0] number_to_bits(6)

stderr的输出是：

Starting var:.. number = 6 15:29:11.327032 call 4 def number_to_bits(number): 15:29:11.327032 line 5 if number: 15:29:11.327032 line 6 bits = [] New var:....... bits = [] 15:29:11.327032 line 7 while number: 15:29:11.327032 line 8 number, remainder = divmod(number, 2) New var:....... remainder = 0 Modified var:.. number = 3 15:29:11.327032 line 9 bits.insert(0, remainder) Modified var:.. bits = [0] 15:29:11.327032 line 7 while number: 15:29:11.327032 line 8 number, remainder = divmod(number, 2) Modified var:.. number = 1 Modified var:.. remainder = 1 15:29:11.327032 line 9 bits.insert(0, remainder) Modified var:.. bits = [1, 0] 15:29:11.327032 line 7 while number: 15:29:11.327032 line 8 number, remainder = divmod(number, 2) Modified var:.. number = 0 15:29:11.327032 line 9 bits.insert(0, remainder) Modified var:.. bits = [1, 1, 0] 15:29:11.327032 line 7 while number: 15:29:11.327032 line 10 return bits 15:29:11.327032 return 10 return bits Return value:.. [1, 1, 0]

2.指定输出内容：

如果不想跟踪整个函数，可以将自己想要跟踪的内容编写在with块中，如下所示，输出lst列表中的最大值、最小值和中间值：

import pysnooper import random def foo(): lst = [] for i in range(10): lst.append(random.randrange(1, 1000)) with pysnooper.snoop(): lower = min(lst) upper = max(lst) mid = (lower + upper) / 2 print(lower, mid, upper) foo()

输出如下：

New var:....... lst = [871, 383, 481, 214, 863, 362, 405, 452, 36, 325] New var:....... i = 9 New var:....... lst = [681, 267, 74, 832, 284, 678, ...] 09:37:35.881721 line 10 lower = min(lst) New var:....... lower = 74 09:37:35.882137 line 11 upper = max(lst) New var:....... upper = 832 09:37:35.882304 line 12 mid = (lower + upper) / 2 74 453.0 832 New var:....... mid = 453.0 09:37:35.882486 line 13 print(lower, mid, upper) 36 453.5 871

3.如果跟踪内容太长，可以将其输出到本地日志文件中

@pysnooper.snoop('/path/to/logfile/file.log')

4.查看一些非局部变量的表达式的值

@pysnooper.snoop(watch=('foo.bar', 'self.x["whatever"]'))

或者查看非局部变量的所有属性列表：

@pysnooper.snoop(watch_explode=('foo', 'self'))

5.跟踪函数中调用的函数

使用depth来设置跟踪的函数调用深度：

@pysnooper.snoop(depth=2)

6.设置一个前缀名，将更容易定位和找到snoop行

@pysnooper.snoop(prefix='ZZZ ')

7.在多线程应用程序上识别哪个线程在输出中被跟踪

@pysnooper.snoop(thread_info=True)

这一项没看懂，有懂的大神，帮忙留言解释一下！