一行代碼干掉 debug 和 print

文 |?某某白米飯

來(lái)源：Python 技術(shù)「ID: pythonall」

在寫算法的時(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?/p>

@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。

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