PySnooper是一個給平民用的調試器,因爲它是完全免費的!使用pysnooper可以完整的輸出函數每一行代碼中的變量的值,供我們去觀察。github網址:PySnooper - Never use print for debugging again
1.示例
下面這個函數的功能是,通過返回一個位列表將數字轉換爲二進制。 然後通過添加@pysnooper.snoop() 裝飾器來追蹤它的每一行的變量的值:
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的輸出是:
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.指定輸出內容:
如果不想跟蹤整個函數,可以將自己想要跟蹤的內容編寫在with塊中,如下所示,輸出lst列表中的最大值、最小值和中間值:
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()
輸出如下:
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.如果跟蹤內容太長,可以將其輸出到本地日誌文件中
@pysnooper.snoop('/path/to/logfile/file.log')
4.查看一些非局部變量的表達式的值
@pysnooper.snoop(watch=('foo.bar', 'self.x["whatever"]'))
或者查看非局部變量的所有屬性列表:
@pysnooper.snoop(watch_explode=('foo', 'self'))
5.跟蹤函數中調用的函數
使用depth來設置跟蹤的函數調用深度:
@pysnooper.snoop(depth=2)
6.設置一個前綴名,將更容易定位和找到snoop行
@pysnooper.snoop(prefix='ZZZ ')
7.在多線程應用程序上識別哪個線程在輸出中被跟蹤
@pysnooper.snoop(thread_info=True)
這一項沒看懂,有懂的大神,幫忙留言解釋一下!