Question

我正在尝试从文件中获取数字，为它们分配变量名称，对变量进行一些数学运算，然后写入文件中的下一行。例如，如果我有一个文件：1 2 3 4 5，这是我到目前为止的缩写代码（Python 3.3）。我遇到的唯一问题是将计算结果写在下一行。预先感谢您的帮助。

with open('test.txt', 'r') as f:
     read_data = f.read()
     a1 = (read_data[0])`a1 = (read_data[0])
print(a1) # this is just a test to see whats happening
f.close()
with open('test.txt','w') as f:
    f.write(a1) #how do I get a1  to write on the next line of the file 
exit()

Answer 1

with open('test.txt', 'r') as f:
    data = f.read()
with open('test.txt', 'w') as f:
    for line in data.split('\n'):
        a1 = line # You didn't specify what modifications you did with the data so...
        f.write(line + '\n')
        f.write(a1 + '\n')

另请注意，我遗漏了f.close()，因为您不需要它忘记它叫什么（上下文管理器旁边的另一个奇特的词），但是with是一个自动关闭语句，每当你离开块f时，Python会自动调用.close()。

既然你没有写下你想要做什么类型的计算，这里有一个例子：

with open('test.txt', 'r') as f:
    data = f.read()
with open('test.txt', 'w') as f:
    for line in data.split('\n'):
        a1 = int(line)*100
        f.write(line + '\n')
        f.write(str(a1) + '\n')

另请阅读下一行中提到的示例，但是您没有指定数据是否已经按行分隔，因此从djas中获取答案可以将这些内容合并到：

with open('test.txt', 'r') as f:
    data = f.read()
with open('test.txt', 'w') as f:
    for line in data.split():
        a1 = int(line)*100
        f.write(line + '\n')
        f.write(str(a1) + '\n')

Answer 2

假设您的输入文件类似于

04 80 52 67

，以下代码有效：

with open('input.txt', 'r') as f:
    line = f.read()

with open('output.txt','w') as f:
    for element in line.split():  
        f.write("%s\n" % ''.join(element))

编辑：您也可以将f.write("%s\n" % ''.join(element))替换为f.write(element+'\n')，并按照@Torxed的建议删除f.close（）。

Answer 3

with open会自动关闭文件，因此您可以在with open语句中执行程序的主要逻辑。例如，该程序将满足您的需求：

with open('test.txt', 'r') as f:
  lines = f.readlines()
newlines = []
for line in lines:
  newlines.append(line)
  newline = #do some logic here
  newlines.append(newline)
with open('test.txt','w') as f:
  for line in newlines:
    f.write(line + '\n')

如果只有一行，您可以取消for line in lines:循环并直接修改文件。

另一方面，如果您希望这是一个迭代过程，如其中一个问题的注释中所示 - 也就是说，您希望新的第二行成为新的第一行，依此类推把上面的内容放在一些函数中如下：

def func(first_line_index):
  """
  Takes the index of the current first line as first_line_index and modifies
  the next line as per your assignment, then writes it back to the file
  """
  with open('test.txt', 'r') as f:
    lines = f.readlines()
  line1 = lines[first_line_index]
  newlines = []
  for line in lines[:first_line_index+1]:
    newlines.append(line)
  newlines.append(lines[first_line_index])
  newline = #do some logic here based on the line above
  newlines.append(newline)
  for line in lines[first_line_index+2:]:
    newlines.append(line)
  with open('test.txt','w') as f:
    for line in newlines:
      f.write(line + '\n')

def __main__():
  counter = 0
  while #some condition- depends on your assignment:
    func(counter)
    counter += 1

写入文件下一行

3 个答案: