I have a file like this:

a
D
c
a
T
c
a
R
c

I want to delete from specific line (in this case 3) until another specific line (in this case 5), so the file would look like:

a
D
c
a
R
c

CodePudding user response：

I prefer to output into another file, so I can debug both input and output files if necessary. If you need to delete in the same file, write to 'my_file.txt' instead of 'my_file2.txt'. The files 'my_file.txt' and 'my_file2.txt' are the input and output respectively in the original question.

with open('my_file.txt') as f:
    lines = f.readlines()
f.close()    

with open('my_file2.txt', 'w') as write_file:
    for i, line in enumerate(lines):
        if i!=2 and i!=3 and i!=4:    #skip lines 3 to 5
            write_file.write(line)
write_file.close()

Edit: On the other hand, if the input list is the following:

andy
David
catherine
anderson
Tera
cathy
angel
Rachel
calvin

You can set the rules for deletion, and run the code

contacts_to_delete = ['catherine', 'Tera', 'angel']

with open('my_file.txt') as f:
    lines = f.readlines()
f.close()

with open('my_file2.txt', 'w') as write_file:
    for contact in lines:
        if contact.strip('\n') not in contacts_to_delete:
            write_file.write(contact)
write_file.close()

Output:

andy
David
anderson
cathy
Rachel
calvin

CodePudding user response：

I think this should work:

def delete_line_range(filename, start_line, end_line):
    # read all lines
    with open(filename, 'r') as f:
        lines = f.readlines()
    f.close()
    with open(filename, 'w') as f:
        # iterate trough lines
        for i in range(len(lines)):
            # check if line is out of range
            if i < start_line or i > end_line:
                f.write(lines[i])
    f.close()
    return

Or if you want to delete multiple ranges

def delete_line_ranges(filename, line_ranges):
    # read all lines
    with open(filename, 'r') as f:
        lines = f.readlines()
    f.close()
    with open(filename, 'w') as f:
        # iterate trough lines
        for i in range(len(lines)):
            # check if line is in range
            in_range = False
            for line_range in line_ranges:
                if i >= line_range[0] and i <= line_range[1]:
                    in_range = True
                    break
            # if not in range, write line
            if not in_range:
                f.write(lines[i])
    f.close()
    return

Where line_ranges is a list of tuples containing start and end line numbers.

Be aware that in both of these functions the line numbers start at 0. Means if you want to delete line 3 to 5 like in your example you need to subtract 1 from both start and end line number.

delete_line_range('test.txt', 2, 4) # deletes line 3 to 5 if you start counting from 1

Edit

Deleting Contacts out of vcf file.

Get range of specific contact:

def get_contact_range(filename, name):
    # read all lines
    with open(filename, 'r') as f:
        lines = f.readlines()
    f.close()
    for i in range(len(lines)):
        # check if line is start of contact
        if lines[i].startswith('BEGIN:VCARD'):
            start_line = i
            continue
        if name in lines[i]:
            for j in range(i, len(lines)):
                # check if line is end of contact
                if lines[j].startswith('END:VCARD'):
                    end_line = j
                    return (start_line, end_line)
    return None
print(get_contact_range('test.vcf', 'John Doe'))

test.vcf

BEGIN:VCARD
VERSION:3.0
PRODID:-//Apple Inc.//macOS 11.5.2//EN
N:Doe;John;;;
FN:John Doe
ORG:Sharpened Productions;
EMAIL;type=INTERNET;type=HOME;type=pref:[email protected]
EMAIL;type=INTERNET;type=WORK:[email protected]
TEL;type=CELL;type=VOICE;type=pref:123-456-7890
ADR;type=HOME;type=pref:;;12345 First Avenue;Hometown;NY;12345;United States
ADR;type=WORK:;;67890 Second Avenue;Businesstown;NY;67890;United States
NOTE:The man I met at the company networking event. He mentioned that he had some potential leads.
item1.URL;type=pref:https://fileinfo.com/
item1.X-ABLabel:_$!!$_
BDAY:2000-01-01
END:VCARD

Output:

(0, 15)

Combine the above functions:

def delete_contact(filename, name):
    # get start and end line of contact
    contact_range = get_contact_range(filename, name)
    # delete contact
    delete_line_range(filename, contact_range[0], contact_range[1])
    return

Multiple Contacts at once:

def delete_contacts(filename, names):
    # get start and end line of contacts
    line_ranges = []
    for name in names:
        contact_range = get_contact_range(filename, name)
        line_ranges.append((contact_range[0], contact_range[1]))
    # delete contacts
    delete_line_ranges(filename, line_ranges)
    return