遍历字符串列表，直到string == newline

Question

I am trying to read selective information from a file. File structure is as follows :

Component1:
   Detail1
   Detail2
   Detail3

Component2:
   Detail1
   Detail2
   Detail3

Component3:
   Detail1
   Detail2
   Detail3

Component4:
   Detail1
   Detail2
   Detail3

File has limited no. of lines and I am reading that file into a list of lines.

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

I want to selectively read information of Component2

So I wrote following code.

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

But it's printing lines till end of list (of lines of file). It's not breaking at 1st occurrence of newline which should be ideally line just before Component3 . (There are no newlines between details of components) Can someone point out what am I doing wrong here?

Answer 1

Using str.startswith() along with a boolean flag:

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

Hence :

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)

OUTPUT :

Component2:
C2_Detail1
C2_Detail2
C2_Detail3

Answer 2

For me this task is simpler if you load text as whole (using read ) rather than as list of lines (using readlines ). I would do it following way:

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])

I assume that there is exactly 1 component fullfilling condition. This solution make described task done, however might be not best if you would need that lines list anyway, so feel free to choose solution best suited for your use case needs.

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'])

This prints:

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