PySnooper库
1. 介绍¶
PySnooper 在 GitHub 上自嘲是一个“乞丐版”调试工具（poor man's debugger）。
一般情况下，在编写 Python 代码时，如果想弄清楚为什么 Python 代码没有按照预期执行、哪些代码在运行哪些没在运行、局部变量又是什么，我们会使用包含断点和观察模式等功能的调试器，或者直接使用 print 语句打印出来。
但上面的方法都比较麻烦，例如使用调试器需要进行繁琐的设置，使用 print 打印也要很仔细。与它们相比，使用 PySnooper 只需为要调试的函数添加一个装饰器即可，这样就能获得运行函数详细的 log，包括执行的代码行和执行时间，以及局部变量发生变化的确切时间。
之所以称为“乞丐版”，相信是因为 PySnooper 使用起来十分简单，开发者可以在任何庞大的代码库中使用它，而无需进行任何设置。只需添加装饰器，并为日志输出地址指定路径。
2. 安装¶
root@leco:~/code/py# pip3 install pysnooper Collecting pysnooper Downloading https://files.pythonhosted.org/packages/82/b8/6838637882b27a32afd67c8a1a83e92ae9c1c05c53a40fc6b0100b4f268d/PySnooper-0.0.38-py2.py3-none-any.whl Installing collected packages: pysnooper Successfully installed pysnooper-0.0.38
3. 测试¶
我们看一下官网的例子
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)
root@leco:~/code/py# python3 demo.py Starting var:.. number = 6 15:21:12.611209 call 4 def number_to_bits(number): 15:21:12.611372 line 5 if number: 15:21:12.611460 line 6 bits = [] New var:....... bits = [] 15:21:12.611540 line 7 while number: 15:21:12.611588 line 8 number, remainder = divmod(number, 2) Modified var:.. number = 3 New var:....... remainder = 0 15:21:12.611677 line 9 bits.insert(0, remainder) Modified var:.. bits = [0] 15:21:12.611739 line 7 while number: 15:21:12.611796 line 8 number, remainder = divmod(number, 2) Modified var:.. number = 1 Modified var:.. remainder = 1 15:21:12.611885 line 9 bits.insert(0, remainder) Modified var:.. bits = [1, 0] 15:21:12.611964 line 7 while number: 15:21:12.612013 line 8 number, remainder = divmod(number, 2) Modified var:.. number = 0 15:21:12.612083 line 9 bits.insert(0, remainder) Modified var:.. bits = [1, 1, 0] 15:21:12.612142 line 7 while number: 15:21:12.612189 line 10 return bits 15:21:12.612237 return 10 return bits Return value:.. [1, 1, 0]
root@leco:~/code/py# cat demo1.py
#!/bin/python
import pysnooper
@pysnooper.snoop()
def add(data):
sum = 0
while data > 0:
sum = sum + data
data = data - 1
return sum
ret = add(3)
print('ret = ',ret)
root@leco:~/code/py# python3 demo1.py
Starting var:.. data = 3
15:27:09.844357 call 5 def add(data):
15:27:09.844510 line 6 sum = 0
New var:....... sum = 0
15:27:09.844649 line 7 while data > 0:
15:27:09.844724 line 8 sum = sum + data
Modified var:.. sum = 3
15:27:09.844805 line 9 data = data - 1
Modified var:.. data = 2
15:27:09.844865 line 7 while data > 0:
15:27:09.844924 line 8 sum = sum + data
Modified var:.. sum = 5
15:27:09.845004 line 9 data = data - 1
Modified var:.. data = 1
15:27:09.845071 line 7 while data > 0:
15:27:09.845130 line 8 sum = sum + data
Modified var:.. sum = 6
15:27:09.845199 line 9 data = data - 1
Modified var:.. data = 0
15:27:09.845256 line 7 while data > 0:
15:27:09.845305 line 10 return sum
15:27:09.845350 return 10 return sum
Return value:.. 6
ret = 6
root@leco:~/code/py# cat demo2.py
#!/bin/python
import pysnooper
@pysnooper.snoop('/tmp/file.log')
def add(data):
sum = 0
while data > 0:
sum = sum + data
data = data - 1
return sum
ret = add(3)
print('ret = ',ret)
root@leco:~/code/py# python3 demo2.py
ret = 6
root@leco:~/code/py# cat /tmp/file.log
Starting var:.. data = 3
15:29:51.102736 call 5 def add(data):
15:29:51.102915 line 6 sum = 0
New var:....... sum = 0
15:29:51.103042 line 7 while data > 0:
15:29:51.103120 line 8 sum = sum + data
Modified var:.. sum = 3
15:29:51.103237 line 9 data = data - 1
Modified var:.. data = 2
15:29:51.103353 line 7 while data > 0:
15:29:51.103427 line 8 sum = sum + data
Modified var:.. sum = 5
15:29:51.103541 line 9 data = data - 1
Modified var:.. data = 1
15:29:51.103654 line 7 while data > 0:
15:29:51.103728 line 8 sum = sum + data
Modified var:.. sum = 6
15:29:51.103840 line 9 data = data - 1
Modified var:.. data = 0
15:29:51.103953 line 7 while data > 0:
15:29:51.104026 line 10 return sum
15:29:51.104100 return 10 return sum
Return value:.. 6
是不是很强大，牛逼不。