Delete a specific string from a list of strings in a file python

Question

I have a list like that:

['Alice,Female,1994\n', 'Bob,Male,1995\n', 'Carol,Male,1993\n', 'Felix,Male,1990\n',     'Giacomo,Male,1990\n', 'Irena,Female,1992\n', 'Joe,Male,1995\n', 'Leo,Male,1995\n', 'Marco,Male,1991\n', 'Tania,Female,1992\n', 'Lillo,Male,1994']

Then I want to remove one string just inserted the name (for example "Lillo") then I want to delete it also from a file. I did something like that but it does not work. I insert the name, looks like it check if the name exist but then, when I ask for showing the file, 'Lillo,Male,1994' is still there. Can you help me? Here is my code:

name = input("Insert the name you want to delete: ")
book = "data.txt"
f = open(book,'r')
line = f.readlines()
f.close()
print(line)
for p in range(len(line)):
    lineString = line[p].split(',')
    if lineString[0] == name:
        line.pop(p)
print(line)

USING THIS CODE FROM @ANON IT WORKS. But how to remove it from the file?

In what way does it not work? Be specific when asking questions like this — Tim
– Tim, Commented Oct 28, 2014 at 21:37

m.wasowski · Accepted Answer · 2014-10-28 22:25:48Z

2

You can just process lines you have read into memory and write them to the file (replacing it's content):

name = input("Insert the name you want to delete: ")
# let's strip excessive whitespace and change to lower case:
name = name.strip().lower()
book = "data.txt"

# use 'with' construct to ensure that file is closed after use:
with open(book, 'r') as f: 
    lines = f.read().splitlines()

filtered = []
for line in lines:
    try: # guard against incorrect record, e.g. 'Guido, 1956'
        name_, sex, year = line.split(',')
    except ValueError:
        print("cannot unpack this line:", line)
        continue
    if name == name_.strip().lower():
        continue # we don't want this line, so we skip it
    filtered.append(line) # line is ok, we keep it

# join list of lines into one string and write to the file:
with open(book, 'w') as f:
    f.write('\n'.join(filtered))

edited Oct 28, 2014 at 22:25

answered Oct 28, 2014 at 22:10

m.wasowski

6,3761 gold badge25 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

pp94 Over a year ago

can you explain what splitlines is? I try it in python and it does not recognized it

pp94 Over a year ago

so maybe I have to import string? Because python says to me AttributeError: 'builtin_function_or_method' object has no attribute 'splitlines'

m.wasowski Over a year ago

sorry, my mistake. it should be f.read().splitlines() of course (already edited)

Joran Beasley · Accepted Answer · 2014-10-28 22:37:58Z

2

never modify a list while iterating over it

instead filter your list

def test(line):
     this_name = line.split(",",1)[0]
     return name == this_name

name = input("Insert the name you want to delete: ")
book = "data.txt"
lines = open(book,'r').readlines()
with open(book,"wb") as f:
    f.write("\n".join( [line for line in lines if test(line)] ))

there is your whole assignment I hope you share with the other kids in your class

edited Oct 28, 2014 at 22:37

answered Oct 28, 2014 at 21:41

Joran Beasley

114k13 gold badges167 silver badges187 bronze badges

3 Comments

pp94 Over a year ago

python gives me an error if I insert this type of text

pp94 Over a year ago

I use the @Anon code and it works but it removes only from the list and not from the file

m.wasowski Over a year ago

OP is using Python 3 (or at least print_function).

alvas · Accepted Answer · 2014-10-28 21:40:23Z

0

In short:

>>> lines = ['Alice,Female,1994\n', 'Bob,Male,1995\n', 'Carol,Male,1993\n', 'Felix,Male,1990\n',     'Giacomo,Male,1990\n', 'Irena,Female,1992\n', 'Joe,Male,1995\n', 'Leo,Male,1995\n', 'Marco,Male,1991\n', 'Tania,Female,1992\n', 'Lillo,Male,1994']
>>> lines = [l.strip() for l in lines]
>>> to_remove = 'Giacomo'
>>> lines_with_removed = [l for l in lines if not l.startswith(to_remove)]
>>> lines_with_removed
['Alice,Female,1994', 'Bob,Male,1995', 'Carol,Male,1993', 'Felix,Male,1990', 'Irena,Female,1992', 'Joe,Male,1995', 'Leo,Male,1995', 'Marco,Male,1991', 'Tania,Female,1992', 'Lillo,Male,1994']

Firstly, when you read a line, the newline character gets read, so you could do this to remove the newline char:

lines = [l.strip() for l in lines]

Next, since the name always comes in the first column of the comma, you could just use:

lines_with_removed = [l for l in lines if not l.startswith(to_remove)]

Alternatively, you could try csv (https://docs.python.org/2/library/csv.html)

answered Oct 28, 2014 at 21:40

alvas

123k118 gold badges503 silver badges806 bronze badges

3 Comments

pp94 Over a year ago

python gives me an error if I insert this type of text

pp94 Over a year ago

Is there the possibility to move the code in python model like I wrote it?

alvas Over a year ago

because you must remove the >>> , type out line by line without the >>>

anon · Accepted Answer · 2014-10-28 21:47:28Z

0

You will also need to open the file for writing if you want to change what's in the file. We can also use range(len()) to go by index value, rather than the line. That'll help with the popping

for p in range(len(line)):
    lineString = line[p].split(',')
    if lineString[0] == name:
        line.pop(p)

So that'll fix that.

Now you want to re-open the file with 'w' permissions to over-write it with the new list using a for-loop.

answered Oct 28, 2014 at 21:47

anon

11

3 Comments

Joran Beasley Over a year ago

no it wont ... it will get bad indexes ... it will work in some instances but the indexing will start skipping entries

pp94 Over a year ago

it technically works because it delete the string but how to delete it also from the file?

Joran Beasley Over a year ago

this is not how you should be doing it .... it will break on one of the cases that your teacher will probably give you

Hackaholic · Accepted Answer · 2014-10-28 22:25:21Z

0

the simple one:

line=['Alice,Female,1994\n', 'Bob,Male,1995\n', 'Carol,Male,1993\n', 'Felix,Male,1990\n',     'Giacomo,Male,1990\n', 'Irena,Female,1992\n', 'Joe,Male,1995\n', 'Leo,Male,1995\n', 'Marco,Male,1991\n', 'Tania,Female,1992\n', 'Lillo,Male,1994']
to_remove = 'carol'
new_line = [ x for x in line if not x.strip().lower().find(to_remove.lower()) ]
new_line

['Alice,Female,1994\n', 'Bob,Male,1995\n', 'Felix,Male,1990\n', 'Giacomo,Male,19 90\n', 'Irena,Female,1992\n', 'Joe,Male,1995\n', 'Leo,Male,1995\n', 'Marco,Male, 1991\n', 'Tania,Female,1992\n', 'Lillo,Male,1994\n']

edited Oct 28, 2014 at 22:25

answered Oct 28, 2014 at 22:19

Hackaholic

19.8k6 gold badges59 silver badges77 bronze badges

2 Comments

m.wasowski Over a year ago

if not to_remove in x.lower() is much simpler... also to_remove.lower returns function, so you'll get an error

Joran Beasley Over a year ago

thats some tricky stuff you are doing with find to ensure it is found at the 0 index ...

Collectives™ on Stack Overflow

Delete a specific string from a list of strings in a file python

5 Answers 5

3 Comments

3 Comments

3 Comments

3 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

3 Comments

3 Comments

3 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related