Python添加了带有标题的新列

Question

我想在现有文件中添加一个新列，并且希望将输出写入另一个文件。我打开文件如下，并添加我所需的语句。如何通过在最后添加新列（使用列名称/标题）将输出写入文件。分离是标签。输入的

with open(newfile, 'w') as outfile: 
    with open(oldfile, 'r', encoding='utf-8') as infile: 
     statements: 

样品：

Col1 Col2 Col3 Col4 

Val1 Val1 Val1 Val1 
Val2 Val2 Val2 Val2 
Val3 Val3 Val3 Val3 
Val4 Val4 Val4 Val4 

输出的样品：

Col1 Col2 Col3 Col4 Col5(Newly added) 

Val1 Val1 Val1 Val1 Val1 
Val2 Val2 Val2 Val2 Val2 
Val3 Val3 Val3 Val3 Val3 
Val4 Val4 Val4 Val4 Val4 

预先感谢。

Answer 1

import csv 

with open('data','r') as f_in: 
    with open('data_out', 'w') as f_out: 
     writer = csv.writer(f_out, delimiter=' ', lineterminator='\n') 
     reader = csv.reader(f_in, delimiter=' ') 

     result = [] 
     # read headers 
     row = next(reader) 
     # add new header to list of headers 
     row.append('Col5') 
     result.append(row) 

     for row in reader: 
      # add new column values 
      row.append(row[0]) 
      result.append(row) 

     writer.writerows(result) 

data_out 

Col1 Col2 Col3 Col4 Col5 
Val1 Val1 Val1 Val1 Val1 
Val2 Val2 Val2 Val2 Val2 
Val3 Val3 Val3 Val3 Val3 
Val4 Val4 Val4 Val4 Val4 

Answer 2

假设您事先知道新列的名称，您可以编写以下代码，如果情况并非如此，您可以在for循环中的first_line条件下计算它。如果您需要其他行为，只需在for循环中更改else部分即可。如果您需要其他行为，请在for循环中更改else部分。

new_column_name = 'Col5' 
with open(newfile, 'w') as outfile: 
    with open(oldfile, 'r', encoding='utf-8') as infile: 
     for line in infile: 
      if first_line: 
       outfile.write('{} {}\n'.format(line, new_column_name)) 
       first_line = False 
      else: 
       values = line.split() 
       if values: 
        values.append(values[-1]) 
       outfile.write(' '.join(values) + '\n') 

希望它能帮助，