CODEWITHSUNDEEP
python
pp94
pp94

Reputation: 133

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

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?

Upvotes: 0

Views: 359

Answers (5)

Joran Beasley
Joran Beasley

Reputation: 113940

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

Upvotes: 2

m.wasowski
m.wasowski

Reputation: 6387

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))

Upvotes: 2

Hackaholic
Hackaholic

Reputation: 19733

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']

Upvotes: 0

anon
anon

Reputation: 11

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.

Upvotes: 0

alvas
alvas

Reputation: 122012

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)

Upvotes: 0

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