如何從循環輸出合併列表Python

Question

Python新手在這裏，

我試圖合併2個列表輸出到for循環中的一個列表。試過append()和extend()無濟於事。

這裏是我的代碼：

c_files =['file1','file2'] 

doc_count = 0 
comb_cran = [] 

for fname in c_files: 
    with open(fname,'r') as cr: 
     cran = cr.read() 

     doc_count = doc_count + 1   
     docID = os.path.basename(fname) 

     #TOKENIZING : 

     # remove SGML Tags 
     removedsgml_cran = BeautifulSoup(cran,"html.parser") 
     clean_cran = removedsgml_cran.get_text() 

     # remove non-alphanumeric 
     non_alpha = re.compile('([^\s\w]|_)+') 
     alpha = non_alpha.sub(' ',clean_cran) 
     alpha_lower = alpha.lower() 

     # word Tokenizing using nltk 
     tokenized = word_tokenize(alpha_lower)     

     # combine the list 
     #comb_cran.extend(tokenized) 

     cword_removed = [(w,docID,1) for w in tokenized if not w in c_words]  

    print(cword_removed) 

，結果：

[('1', 'cranfield0001', 1), ('experimental', 'cranfield0001', 1), ('investigation', 'cranfield0001', 1), ('aerodynamics', 'cranfield0001', 1), ('slipstream', 'cranfield0001', 1), ('brenckman', 'cranfield0001', 1), ('ae', 'cranfield0001', 1), ('scs', 'cranfield0001', 1), ('25', 'cranfield0001', 1), ('1958', 'cranfield0001', 1), ('324', 'cranfield0001', 1), ('experimental', 'cranfield0001', 1), ('study', 'cranfield0001', 1), ('propeller', 'cranfield0001', 1), ('slipstream', 'cranfield0001', 1), ('made', 'cranfield0001', 1), ('order', 'cranfield0001', 1), ('determine', 'cranfield0001', 1), ('spanwise', 'cranfield0001', 1), ('distribution', 'cranfield0001', 1), ('lift', 'cranfield0001', 1), ('increase', 'cranfield0001', 1), ('due', 'cranfield0001', 1), ('slipstream', 'cranfield0001', 1), ('angles', 'cranfield0001', 1), ('attack', 'cranfield0001', 1), ('free', 'cranfield0001', 1), ('stream', 'cranfield0001', 1), ('slipstream', 'cranfield0001', 1), ('velocity', 'cranfield0001', 1), ('ratios', 'cranfield0001', 1), ('results', 'cranfield0001', 1), ('intended', 'cranfield0001', 1), ('evaluation', 'cranfield0001', 1), ('basis', 'cranfield0001', 1), ('theoretical', 'cranfield0001', 1), ('treatments', 'cranfield0001', 1), ('problem', 'cranfield0001', 1), ('comparative', 'cranfield0001', 1), ('span', 'cranfield0001', 1), ('loading', 'cranfield0001', 1), ('curves', 'cranfield0001', 1), ('supporting', 'cranfield0001', 1), ('evidence', 'cranfield0001', 1), ('showed', 'cranfield0001', 1), ('substantial', 'cranfield0001', 1), ('lift', 'cranfield0001', 1), ('increment', 'cranfield0001', 1), ('produced', 'cranfield0001', 1), ('slipstream', 'cranfield0001', 1), ('due', 'cranfield0001', 1), ('destalling', 'cranfield0001', 1), ('boundary', 'cranfield0001', 1), ('layer', 'cranfield0001', 1), ('control', 'cranfield0001', 1), ('effect', 'cranfield0001', 1), ('integrated', 'cranfield0001', 1), ('remaining', 'cranfield0001', 1), ('lift', 'cranfield0001', 1), ('increment', 'cranfield0001', 1), ('subtracting', 'cranfield0001', 1), ('destalling', 'cranfield0001', 1), ('lift', 'cranfield0001', 1), ('found', 'cranfield0001', 1), ('agree', 'cranfield0001', 1), ('potential', 'cranfield0001', 1), ('flow', 'cranfield0001', 1), ('theory', 'cranfield0001', 1), ('empirical', 'cranfield0001', 1), ('evaluation', 'cranfield0001', 1), ('destalling', 'cranfield0001', 1), ('effects', 'cranfield0001', 1), ('made', 'cranfield0001', 1), ('specific', 'cranfield0001', 1), ('configuration', 'cranfield0001', 1), ('experiment', 'cranfield0001', 1)] 


[('2', 'cranfield0002', 1), ('simple', 'cranfield0002', 1), ('shear', 'cranfield0002', 1), ('flow', 'cranfield0002', 1), ('past', 'cranfield0002', 1), ('flat', 'cranfield0002', 1), ('plate', 'cranfield0002', 1), ('incompressible', 'cranfield0002', 1), ('fluid', 'cranfield0002', 1), ('small', 'cranfield0002', 1), ('viscosity', 'cranfield0002', 1), ('yili', 'cranfield0002', 1), ('department', 'cranfield0002', 1), ('aeronautical', 'cranfield0002', 1), ('engineering', 'cranfield0002', 1), ('rensselaer', 'cranfield0002', 1), ('polytechnic', 'cranfield0002', 1), ('institute', 'cranfield0002', 1), ('troy', 'cranfield0002', 1), ('study', 'cranfield0002', 1), ('high', 'cranfield0002', 1), ('speed', 'cranfield0002', 1), ('viscous', 'cranfield0002', 1), ('flow', 'cranfield0002', 1), ('past', 'cranfield0002', 1), ('dimensional', 'cranfield0002', 1), ('curved', 'cranfield0002', 1), ('shock', 'cranfield0002', 1), ('wave', 'cranfield0002', 1), ('emitting', 'cranfield0002', 1), ('nose', 'cranfield0002', 1), ('leading', 'cranfield0002', 1), ('edge', 'cranfield0002', 1), ('exists', 'cranfield0002', 1), ('inviscid', 'cranfield0002', 1), ('rotational', 'cranfield0002', 1), ('flow', 'cranfield0002', 1), ('region', 'cranfield0002', 1), ('shock', 'cranfield0002', 1), ('wave', 'cranfield0002', 1), ('boundary', 'cranfield0002', 1), ('layer', 'cranfield0002', 1), ('situation', 'cranfield0002', 1), ('arises', 'cranfield0002', 1), ('instance', 'cranfield0002', 1), ('study', 'cranfield0002', 1), ('hypersonic', 'cranfield0002', 1), ('viscous', 'cranfield0002', 1), ('flow', 'cranfield0002', 1), ('past', 'cranfield0002', 1), ('flat', 'cranfield0002', 1), ('plate', 'cranfield0002', 1), ('situation', 'cranfield0002', 1), ('prandtl', 'cranfield0002', 1), ('classical', 'cranfield0002', 1), ('boundary', 'cranfield0002', 1), ('layer', 'cranfield0002', 1), ('problem', 'cranfield0002', 1), ('prandtl', 'cranfield0002', 1), ('original', 'cranfield0002', 1), ('problem', 'cranfield0002', 1), ('inviscid', 'cranfield0002', 1), ('free', 'cranfield0002', 1), ('stream', 'cranfield0002', 1), ('boundary', 'cranfield0002', 1), ('layer', 'cranfield0002', 1), ('irrotational', 'cranfield0002', 1), ('hypersonic', 'cranfield0002', 1), ('boundary', 'cranfield0002', 1), ('layer', 'cranfield0002', 1), ('problem', 'cranfield0002', 1), ('inviscid', 'cranfield0002', 1), ('free', 'cranfield0002', 1), ('stream', 'cranfield0002', 1), ('considered', 'cranfield0002', 1), ('rotational', 'cranfield0002', 1), ('effects', 'cranfield0002', 1), ('vorticity', 'cranfield0002', 1), ('recently', 'cranfield0002', 1), ('discussed', 'cranfield0002', 1), ('ferri', 'cranfield0002', 1), ('libby', 'cranfield0002', 1), ('present', 'cranfield0002', 1), ('paper', 'cranfield0002', 1), ('simple', 'cranfield0002', 1), ('shear', 'cranfield0002', 1), ('flow', 'cranfield0002', 1), ('past', 'cranfield0002', 1), ('flat', 'cranfield0002', 1), ('plate', 'cranfield0002', 1), ('fluid', 'cranfield0002', 1), ('small', 'cranfield0002', 1), ('viscosity', 'cranfield0002', 1), ('investigated', 'cranfield0002', 1), ('shown', 'cranfield0002', 1), ('problem', 'cranfield0002', 1), ('treated', 'cranfield0002', 1), ('boundary', 'cranfield0002', 1), ('layer', 'cranfield0002', 1), ('approximation', 'cranfield0002', 1), ('feature', 'cranfield0002', 1), ('free', 'cranfield0002', 1), ('stream', 'cranfield0002', 1), ('constant', 'cranfield0002', 1), ('vorticity', 'cranfield0002', 1), ('discussion', 'cranfield0002', 1), ('restricted', 'cranfield0002', 1), ('dimensional', 'cranfield0002', 1), ('incompressible', 'cranfield0002', 1), ('steady', 'cranfield0002', 1), ('flow', 'cranfield0002', 1)] 

的結果是正確的，但他們是從各個線圈印刷單獨的列表。 我需要他們在一個列表中。

我試圖把打印的循環之外，然後它只打印第二個列表。

Answer 1

當你遍歷文件時，你會得到每個文件列表。您可以使用驚人的簡單運算符'+'輕鬆地組合列表。你的正確的代碼是：

c_files =['file1','file2'] 

doc_count = 0 
comb_cran = []  
total_list=[] #Your final wanted list 

for fname in c_files: 
    with open(fname,'r') as cr: 
     ...your codes 

     #Combine the list by simple '+' operator 
     total_list = total_list+[(w,docID,1) for w in tokenized if not w in c_words]  

    print(cword_removed) 

Answer 2

所以在這裏你遇到了堆棧和一個叫作範圍的概念。

在你的程序中，有問題的列表是cword_removed。您只需在循環中聲明並初始化它。當您的程序第一次到達cword_removed時，它會創建一個類型爲list的變量並使用您定義的列表理解來填充它。當程序第二次繞過循環時，它會用新值覆蓋變量！這是因爲局部變量cword_removed完全在循環的範圍內。

爲了解決這個問題，通過列表解析聲明環以外的變量，增量：

c_files =['file1','file2'] 

doc_count = 0 
comb_cran = [] 
cword_removed = [] 

for fname in c_files: 
    with open(fname,'r') as cr: 
    . 
    . # the rest of your code 
    . 
    cword_removed += [(w,docID,1) for w in tokenized if not w in c_words] 

Answer 3

你每次只需重寫你的清單，然後打印新的。您可以添加列表。在循環前定義你的列表，並使用full_list += new_list將新列表添加到已有的列表中。並將最終的打印語句放在for循環之外。

c_files =['file1','file2'] 

doc_count = 0 
comb_cran = [] 
cword_removed = [] 


for fname in c_files: 
    with open(fname,'r') as cr: 
     cran = cr.read() 

     doc_count = doc_count + 1   
     docID = os.path.basename(fname) 

     #TOKENIZING : 

     # remove SGML Tags 
     removedsgml_cran = BeautifulSoup(cran,"html.parser") 
     clean_cran = removedsgml_cran.get_text() 

     # remove non-alphanumeric 
     non_alpha = re.compile('([^\s\w]|_)+') 
     alpha = non_alpha.sub(' ',clean_cran) 
     alpha_lower = alpha.lower() 

     # word Tokenizing using nltk 
     tokenized = word_tokenize(alpha_lower)     

     # combine the list 
     #comb_cran.extend(tokenized) 

     cword_removed += [(w,docID,1) for w in tokenized if not w in c_words]  

print(cword_removed)