Question

我正在尝试从文件中读取选择性信息。文件结构如下：

Component1:
   Detail1
   Detail2
   Detail3

Component2:
   Detail1
   Detail2
   Detail3

Component3:
   Detail1
   Detail2
   Detail3

Component4:
   Detail1
   Detail2
   Detail3

文件没有限制。行，我正在将该文件读入行列表。

with open('/tmp/filename.txt', 'r') as openf:
            for line_no, line in enumerate(openf):
                file_lines_list.append(line)

我想选择性地读取 Component2

的信息

所以我写了以下代码。

with open('/tmp/filename.txt', 'r') as f:
                for line_no, line in enumerate(f):
                    if "Component2" in line:
                       x = line_no
                       print(x)
                       for item in file_lines_list[x:]:
                           if item != "\n":   
                              tmp_file.write(item)
                           else:
                              break

但是它正在打印行，直到列表末尾（文件行）。它不会在第一次出现换行符时中断，理想情况下应该是 Component3 之前的行。（组件详细信息之间没有换行符）有人可以指出我在做什么错吗？

Answer 1

使用str.startswith()和一个布尔标志：

list.txt ：

Component1:
   C1_Detail1
   C1_Detail2
   C1_Detail3

Component2:
   C2_Detail1
   C2_Detail2
   C2_Detail3

Component3:
   C3_Detail1
   C3_Detail2
   C3_Detail3

Component4:
   C4_Detail1
   C4_Detail2
   C4_Detail3

因此：

with open('list.txt', 'r') as f:
    content = f.readlines()

# you may also want to remove empty lines
content = [l.strip() for l in content if l.strip()]
bFlag = False
for line in content:
    if line.startswith('Component2'):
        bFlag = not bFlag
    if bFlag:
        if 'Component3' in line:
            break
        else:
            print(line)

输出：

Component2:
C2_Detail1
C2_Detail2
C2_Detail3

Answer 2

对我来说，如果您整体加载文本（使用read，而不是行列表（使用readlines），则此任务会更简单。我会按照以下方式进行操作：

with open('input_file.txt','r') as openf:
    data = openf.read()
components = data.split('\n\n')
components = [i for i in components if i.startswith('Component2')]
print(len(components)) #prints 1 as expected
with open('out_file.txt','w') as f:
    f.write(components[0])

我假设组件完全充满了1个条件。该解决方案可以完成描述的任务，但是如果您仍然需要该行列表，则可能不是最好的选择，因此可以随时选择最适合您的用例需求的解决方案。

Answer 3

with open('file') as file:
    # remove empty lines
    lines = [line for line in file.readlines() if line]

    # holds all our components
    components = {}
    # holds the last component
    comp_name = None
    for line in lines:
        if not line.startswith('   '):
            # remove : from the end for easy reference
            comp_name = line[:-1]
            # add new Component our map
            components[comp_name] = []
        else:
            # add detail to component that already exists
            components[comp_name].append(line.strip())

    # now we just find our component
    print(components['Component2'])

此打印：

['Detail1', 'Detail2', 'Detail3']

遍历字符串列表，直到string == newline

3 个答案: