作者：某某白米飯

來(lái)源：Python 技術(shù)

在寫(xiě)算法的時(shí)候，總是要每行每個(gè)變量一個(gè)個(gè)的 debug，有時(shí)候還要多寫(xiě)幾個(gè) print，一道算法題要花好長(zhǎng)時(shí)間才能理解。pysnooper 模塊可以把在運(yùn)行中變量值都給打印出來(lái)。

模塊安裝

pip3 install pysnooper

簡(jiǎn)單例子

下面是道簡(jiǎn)單的力扣算法題作為一個(gè)簡(jiǎn)單的例子

import pysnooper @pysnooper.snoop() def longestCommonPrefix(strs): res = '' for i in zip(*strs):
        print(i) if len(set(i)) == 1:
            res += i[0] else break return res if __name__ == 'main':
    longestCommonPrefix(["flower","flow","flight"])

結(jié)果：

3:38:25.863579 call 4 def longestCommonPrefix(strs): 23:38:25.864474 line 5 res = '' New var:....... res = '' 23:38:25.864474 line 6 for i in zip(*strs): New var:....... i = ('f', 'f', 'f') 23:38:25.865479 line 7 print(i)
('f', 'f', 'f') 23:38:25.866471 line 8 if len(set(i))==1: 23:38:25.866471 line 9 res+=i[0]
Modified var:.. res = 'f' 23:38:25.866471 line 6 for i in zip(*strs):
Modified var:.. i = ('l', 'l', 'l') 23:38:25.866471 line 7 print(i)
('l', 'l', 'l') 23:38:25.867468 line 8 if len(set(i))==1: 23:38:25.867468 line 9 res+=i[0]
Modified var:.. res = 'fl' 23:38:25.868476 line 6 for i in zip(*strs):
Modified var:.. i = ('o', 'o', 'i') 23:38:25.868476 line 7 print(i)
('o', 'o', 'i') 23:38:25.869463 line 8 if len(set(i))==1: 23:38:25.869463 line 11 break 23:38:25.869463 line 12 return res 23:38:25.869463 return 12 return res Return value:.. 'fl' Elapsed time: 00:00:00.008201 

我們可以看到 pysnooper 把整個(gè)執(zhí)行程序都記錄了下來(lái)，其中包括行號(hào)， 行內(nèi)容，變量的結(jié)果等情況，我們很容易的就看懂了這個(gè)算法的真實(shí)情況。并且不需要再使用 debug 和 print 調(diào)試代碼。很是省時(shí)省力，只需要在方法上面加一行 @pysnooper.snoop()。

復(fù)雜使用

pysnooper 包含了多個(gè)參數(shù)，一起來(lái)看看吧

output

output 默認(rèn)輸出到控制臺(tái)，設(shè)置后輸出到文件，在服務(wù)器中運(yùn)行的時(shí)候，特定的時(shí)間出現(xiàn)代碼問(wèn)題就很容易定位錯(cuò)誤了，不然容易抓瞎。小編在實(shí)際中已經(jīng)被這種問(wèn)題困擾了好幾次，每次都掉好多頭發(fā)。

@pysnooper.snoop('D:pysnooper.log') def longestCommonPrefix(strs):

示例結(jié)果:

watch 和 watch_explode

watch 用來(lái)設(shè)置跟蹤的非局部變量，watch_explode 表示設(shè)置的變量都不監(jiān)控，只監(jiān)控沒(méi)設(shè)置的變量，正好和 watch 相反。

index = 1 @pysnooper.snoop(watch=('index')) def longestCommonPrefix(strs):

示例結(jié)果

沒(méi)有加 watch 參數(shù)

Starting var:.. strs = ['flower', 'flow', 'flight'] 00:12:33.715367 call 5 def longestCommonPrefix(strs):
00:12:33.717324 line         7     res = '' New var:....... res = '' 

加了watch 參數(shù)，就會(huì)有一個(gè) Starting var:.. index

Starting var:.. strs = ['flower', 'flow', 'flight']
Starting var:.. index = 1 00:10:35.151036 call 5 def longestCommonPrefix(strs):
00:10:35.151288 line         7     res = '' New var:....... res = '' 

depth

depth 監(jiān)控函數(shù)的深度

@pysnooper.snoop(depth=2) def longestCommonPrefix(strs): otherMethod()

示例結(jié)果

Starting var:.. strs = ['flower', 'flow', 'flight'] 00:20:54.059803 call 5 def longestCommonPrefix(strs): 00:20:54.059803 line 6 otherMethod() 00:20:54.060785 call 16 def otherMethod(): 00:20:54.060785 line 17 x = 1 New var:....... x = 1 00:20:54.060785 line 18 x = x + 1 Modified var:.. x = 2 00:20:54.060785 return 18 x = x + 1 Return value:.. None 00:20:54.061782 line 7 res = '' 

監(jiān)控的結(jié)果顯示，當(dāng)監(jiān)控到調(diào)用的函數(shù)的時(shí)候，記錄上會(huì)加上縮進(jìn)，并將它的局部變量和返回值打印處理。

prefix

prefix 輸出內(nèi)容的前綴

@pysnooper.snoop(prefix='-------------') def longestCommonPrefix(strs):

示例結(jié)果

-------------Starting var:.. strs = ['flower', 'flow', 'flight']
-------------00:39:13.986741 call 5 def longestCommonPrefix(strs): -------------00:39:13.987218 line 6 res = '' 

relative_time

relative_time 代碼運(yùn)行的時(shí)間

@pysnooper.snoop(relative_time=True) def longestCommonPrefix(strs): 

示例結(jié)果

Starting var:.. strs = ['flower', 'flow', 'flight'] 00:00:00.000000 call 5 def longestCommonPrefix(strs):
00:00:00.001998 line         6     res = '' New var:....... res = '' 00:00:00.001998 line 7 for i in zip(*strs): 

max_variable_length

max_variable_length 輸出的變量和異常的最大長(zhǎng)度，默認(rèn)是 100 個(gè)字符，超過(guò) 100 個(gè)字符就會(huì)被截?cái)?，可以設(shè)置為 max_variable_length=None 不截?cái)噍敵?/span>

@pysnooper.snoop(max_variable_length=5) def longestCommonPrefix(strs): 

示例結(jié)果

Starting var:.. strs = [...]
00:56:44.343639 call 5 def longestCommonPrefix(strs): 00:56:44.344696 line 6 res = '' New var:....... res = '' 00:56:44.344696 line 7 for i in zip(*strs): New var:....... i = (...)

總結(jié)

本文介紹了怎么使用 pysnooper 工具，pysnooper 不僅可以少一些 debug 和 print，更能幫助理解算法題。