如何从循环输出Python中合并列表答案

【问题标题】：how to merge lists from a loop output Python如何从循环输出Python中合并列表
【发布时间】：2018-03-07 13:30:55
【问题描述】：

我正在尝试将 2 个列表输出合并到一个来自 for 循环的列表中。尝试append() 和extend() 无济于事。

这是我的代码：

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)

结果：

[('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)]

结果是正确的，但是它们是从每个循环打印的单独列表。我需要将它们放在一个列表中。

我尝试将打印放在循环之外，然后它只打印第二个列表。

【问题讨论】：

你试过list1 + list2吗？
你可以尝试使用zip。如果你想在一个又一个列表中实现，那么使用 list.append(element) 作为 secondListElements 中的元素

标签： python list loops merge

【解决方案1】：

您只是每次都覆盖您的列表，然后打印新的列表。您可以添加列表。在循环之前定义您的列表，然后使用full_list += new_list 将新列表添加到已经存在的列表中。并将最终的打印语句放在 for 循环之外。

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)

【讨论】：

【解决方案2】：

所以你在这里遇到了堆栈和一个叫做作用域的概念。

在您的程序中，有问题的列表是cword_removed。您只需在循环中声明和初始化它。当您的程序第一次到达cword_removed 时，它会创建一个list 类型的变量，并使用您定义的列表推导填充它。当程序第二次循环时，它会用新值覆盖变量！那是因为局部变量cword_removed 完全在循环的范围内。

为了解决这个问题，在循环外声明变量，并通过列表推导递增：

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]

【讨论】：

我想知道如何将 c_files = ['file1','file2'] 概括为已知（大量）条目。它不仅仅是一个 numpy 数组，这将是磨损的数据类型（我认为 - 这里也是一个 python 新手！）

【解决方案3】：

当您遍历文件时，您将获得一个文件的每个列表。您可以使用惊人的简单运算符“+”轻松组合列表。您正确的代码是：

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)

【讨论】：