I want to open a file, search for a specific word, change the word and save the file again. Sounds really easy - but I just can't get it working... I know that I have to overwrite the whole file but only change this one word!
My Code:
f = open('./myfile', 'r')
linelist = f.readlines()
f.close
for line in linelist:
i =0;
if 'word' in line:
for number in arange(0,1,0.1)):
myNumber = 2 - number
myNumberasString = str(myNumber)
myChangedLine = line.replace('word', myNumberasString)
f2 = open('./myfile', 'w')
f2.write(line)
f2.close
#here I have to do some stuff with these files so there is a reason
#why everything is in this for loop. And I know that it will
#overwrite the file every loop and that is good so. I want that :)
If I make it like this, the 'new' myfile file contains only the changed line. But I want the whole file with the changed line... Can anyone help me?
****EDIT*****
I fixed it! I just turned the loops around and now it works perfectly like this:
f=open('myfile','r')
text = f.readlines()
f.close()
i =0;
for number in arange(0,1,0.1):
fw=open('mynewfile', 'w')
myNumber = 2 - number
myNumberasString = str(myNumber)
for line in text:
if 'word' in line:
line = line.replace('word', myNumberasString)
fw.write(line)
fw.close()
#do my stuff here where I need all these input files
You just need to write out all the other lines as you go. As I said in my comment, I don't know what you are really trying to do with your replace, but here's a slightly simplified version in which we're just replacing all occurrences of 'word' with 'new':
f = open('./myfile', 'r')
linelist = f.readlines()
f.close
# Re-open file here
f2 = open('./myfile', 'w')
for line in linelist:
line = line.replace('word', 'new')
f2.write(line)
f2.close()
Or using contexts:
with open('./myfile', 'r') as f:
lines = f.readlines()
with open('./myfile', 'w') as f:
for line in lines:
line = line.replace('word', 'new')
f.write(line)
Use fileinput passing in whatever you want to replace:
import fileinput
for line in fileinput.input("in.txt",inplace=True):
print(line.replace("whatever","foo"),end="")
You don't seem to be doing anything special in your loop that cannot be calculated first outside the loop, so create the string you want to replace the word with and pass it to replace.
inplace=True will mean the original file is changed. If you want to verify everything looks ok then remove the inplace=True for the first run and you will actually see the replaced output instead of the lines being written to the file.
If you want to write to a temporary file, you can use a NamedTemporaryFile with shutil.move:
from tempfile import NamedTemporaryFile
from shutil import move
with open("in.txt") as f, NamedTemporaryFile(dir=".",delete=False) as out:
for line in f:
out.write(line.replace("whatever","foo"))
move("in.txt",out.name)
One problem you may encounter is matching substrings with replace so if you know the word is always followed in the middle of a sentence surrounded by whitespace you could add that but if not you will need to split and check every word.
from tempfile import NamedTemporaryFile
from shutil import move
from string import punctuation
with open("in.txt") as f, NamedTemporaryFile(dir=".",delete=False) as out:
for line in f:
out.write(" ".join(word if word.strip(punctuation) != "whatever" else "foo"
for word in line.split()))
The are three issues with your current code. First, create the f2 file handle before starting the loop, otherwise you'll overwrite the file in each iteration. Third, you are writing an unmodified line in f2.write(line). I guess you meant f2.write(myChangedLine)? Third, you should add an else statement that writes unmodified lines to the file. So:
f = open('./myfile', 'r')
linelist = f.readlines()
f.close
f2 = open('./myfile', 'w')
for line in linelist:
i =0;
if 'word' in line:
for number in arange(0,1,0.1)):
myNumber = 2 - number
myNumberasString = str(myNumber)
myChangedLine = line.replace('word', myNumberasString)
f2.write(myChangedLine)
else:
f2.write(line)
f2.close()
Related
I am trying to write words from words.txt to newfile.txt using python3, with a format like this:
words.txt:
Hello
I
am
a
file
and I want the word Morning added between each new word in words.txt, inside a new file called newfile.txt.
so newfile.txt should look like this:
Hello
Morning
I
Morning
Am
Morning
A
Morning
File
Does anyone know how to do this?
Sorry about the bad phrasing,
Gomenburu
To avoid blowing main memory for a large file, you'd want to insert the extra strings as you go. It's not hard, just a little tricky to ensure they only go between existing lines, not at the beginning or end:
# Open both files
with open('words.txt') as inf, open('newfile.txt', 'w') as outf:
outf.write(next(inf)) # Copy over first line without preceding "Morning"
for line in inf: # Lazily pull remaining lines from infile one by one
outf.write("Morning\n") # Write the in-between "Morning" before each new line
outf.write(line) # Write pre-existing line
with open("words.txt", "r") as words_file, open("newfile.txt", "w") as new_words_file:
new_words_file.write("\n".join([f"{word}\nMorning" for word in words_file.read().split("\n")]))
with open('words.txt') as f:
lines = f.readlines()
for i in range(len(lines)):
a = lines[i] + 'Morning' + '\n'
with open('newfile.txt','a') as file:
file.write(a)
file.close()
This should do it!
I would start with this:
f1 = open( 'words.txt')
f2 = open( 'newfile.txt')
lines = f1.readlines()
for line in lines:
f2.write( line + "Morning\n")
f2.close()
I'm trying to delete each line which contains "annote = {" but my code is not working.
I have a file stored in a variable myFile and I want to go through every line of this file and delete every line which contains the string annote.
this is basically my code:
print(myFile.read()) //prints myFile
myFile.seek(0)
for lines in myFile:
if b"annote = {" in lines:
lines = lines.replace(b'.', b'')
myFile.seek(0)
print(myFile.read()) //this prints the exact same as the print method above so annote lines
//haven't been removed from this file
I have no idea why annote lines doesn't get removed. There is probably anything wrong with the replace method because it always is inside the if request but nothing happens with annote lines. I've also tried lines.replace(b'.', b'') instead of lines = lines.replace(b'.', b'') but nothing happened.
Hope anyone can help me with this problem
This will do it for you.
f.readlines() returns a list of text lines
Then you check for the lines that do not contain the things you do not want
Then you write them to a separate new file.
f2 = open('newtextfile.txt', 'w')
with open('text_remove_line.txt', 'r') as f:
for line in f.readlines():
if 'annote = {' not in line:
f2.write(line)
f2.close()
This should work:
with open('input.txt') as fin :
lines = fin.read().split('\n') # read the text, split into the lines
with open('output.txt', 'w') as fout :
# write out only the lines that does not contain the text 'annote = {'
fout.write( '\n'.join( [i for i in lines if i.find('annote = {') == -1] ))
Let's say I have a text file full of nicknames. How can I delete a specific nickname from this file, using Python?
First, open the file and get all your lines from the file. Then reopen the file in write mode and write your lines back, except for the line you want to delete:
with open("yourfile.txt", "r") as f:
lines = f.readlines()
with open("yourfile.txt", "w") as f:
for line in lines:
if line.strip("\n") != "nickname_to_delete":
f.write(line)
You need to strip("\n") the newline character in the comparison because if your file doesn't end with a newline character the very last line won't either.
Solution to this problem with only a single open:
with open("target.txt", "r+") as f:
d = f.readlines()
f.seek(0)
for i in d:
if i != "line you want to remove...":
f.write(i)
f.truncate()
This solution opens the file in r/w mode ("r+") and makes use of seek to reset the f-pointer then truncate to remove everything after the last write.
The best and fastest option, rather than storing everything in a list and re-opening the file to write it, is in my opinion to re-write the file elsewhere.
with open("yourfile.txt", "r") as file_input:
with open("newfile.txt", "w") as output:
for line in file_input:
if line.strip("\n") != "nickname_to_delete":
output.write(line)
That's it! In one loop and one only you can do the same thing. It will be much faster.
This is a "fork" from #Lother's answer (which I believe that should be considered the right answer).
For a file like this:
$ cat file.txt
1: october rust
2: november rain
3: december snow
This fork from Lother's solution works fine:
#!/usr/bin/python3.4
with open("file.txt","r+") as f:
new_f = f.readlines()
f.seek(0)
for line in new_f:
if "snow" not in line:
f.write(line)
f.truncate()
Improvements:
with open, which discard the usage of f.close()
more clearer if/else for evaluating if string is not present in the current line
The issue with reading lines in first pass and making changes (deleting specific lines) in the second pass is that if you file sizes are huge, you will run out of RAM. Instead, a better approach is to read lines, one by one, and write them into a separate file, eliminating the ones you don't need. I have run this approach with files as big as 12-50 GB, and the RAM usage remains almost constant. Only CPU cycles show processing in progress.
I liked the fileinput approach as explained in this answer:
Deleting a line from a text file (python)
Say for example I have a file which has empty lines in it and I want to remove empty lines, here's how I solved it:
import fileinput
import sys
for line_number, line in enumerate(fileinput.input('file1.txt', inplace=1)):
if len(line) > 1:
sys.stdout.write(line)
Note: The empty lines in my case had length 1
If you use Linux, you can try the following approach.
Suppose you have a text file named animal.txt:
$ cat animal.txt
dog
pig
cat
monkey
elephant
Delete the first line:
>>> import subprocess
>>> subprocess.call(['sed','-i','/.*dog.*/d','animal.txt'])
then
$ cat animal.txt
pig
cat
monkey
elephant
Probably, you already got a correct answer, but here is mine.
Instead of using a list to collect unfiltered data (what readlines() method does), I use two files. One is for hold a main data, and the second is for filtering the data when you delete a specific string. Here is a code:
main_file = open('data_base.txt').read() # your main dataBase file
filter_file = open('filter_base.txt', 'w')
filter_file.write(main_file)
filter_file.close()
main_file = open('data_base.txt', 'w')
for line in open('filter_base'):
if 'your data to delete' not in line: # remove a specific string
main_file.write(line) # put all strings back to your db except deleted
else: pass
main_file.close()
Hope you will find this useful! :)
I think if you read the file into a list, then do the you can iterate over the list to look for the nickname you want to get rid of. You can do it much efficiently without creating additional files, but you'll have to write the result back to the source file.
Here's how I might do this:
import, os, csv # and other imports you need
nicknames_to_delete = ['Nick', 'Stephen', 'Mark']
I'm assuming nicknames.csv contains data like:
Nick
Maria
James
Chris
Mario
Stephen
Isabella
Ahmed
Julia
Mark
...
Then load the file into the list:
nicknames = None
with open("nicknames.csv") as sourceFile:
nicknames = sourceFile.read().splitlines()
Next, iterate over to list to match your inputs to delete:
for nick in nicknames_to_delete:
try:
if nick in nicknames:
nicknames.pop(nicknames.index(nick))
else:
print(nick + " is not found in the file")
except ValueError:
pass
Lastly, write the result back to file:
with open("nicknames.csv", "a") as nicknamesFile:
nicknamesFile.seek(0)
nicknamesFile.truncate()
nicknamesWriter = csv.writer(nicknamesFile)
for name in nicknames:
nicknamesWriter.writeRow([str(name)])
nicknamesFile.close()
In general, you can't; you have to write the whole file again (at least from the point of change to the end).
In some specific cases you can do better than this -
if all your data elements are the same length and in no specific order, and you know the offset of the one you want to get rid of, you could copy the last item over the one to be deleted and truncate the file before the last item;
or you could just overwrite the data chunk with a 'this is bad data, skip it' value or keep a 'this item has been deleted' flag in your saved data elements such that you can mark it deleted without otherwise modifying the file.
This is probably overkill for short documents (anything under 100 KB?).
I like this method using fileinput and the 'inplace' method:
import fileinput
for line in fileinput.input(fname, inplace =1):
line = line.strip()
if not 'UnwantedWord' in line:
print(line)
It's a little less wordy than the other answers and is fast enough for
Save the file lines in a list, then remove of the list the line you want to delete and write the remain lines to a new file
with open("file_name.txt", "r") as f:
lines = f.readlines()
lines.remove("Line you want to delete\n")
with open("new_file.txt", "w") as new_f:
for line in lines:
new_f.write(line)
here's some other method to remove a/some line(s) from a file:
src_file = zzzz.txt
f = open(src_file, "r")
contents = f.readlines()
f.close()
contents.pop(idx) # remove the line item from list, by line number, starts from 0
f = open(src_file, "w")
contents = "".join(contents)
f.write(contents)
f.close()
You can use the re library
Assuming that you are able to load your full txt-file. You then define a list of unwanted nicknames and then substitute them with an empty string "".
# Delete unwanted characters
import re
# Read, then decode for py2 compat.
path_to_file = 'data/nicknames.txt'
text = open(path_to_file, 'rb').read().decode(encoding='utf-8')
# Define unwanted nicknames and substitute them
unwanted_nickname_list = ['SourDough']
text = re.sub("|".join(unwanted_nickname_list), "", text)
Do you want to remove a specific line from file so use this snippet short and simple code you can easily remove any line with sentence or prefix(Symbol).
with open("file_name.txt", "r") as f:
lines = f.readlines()
with open("new_file.txt", "w") as new_f:
for line in lines:
if not line.startswith("write any sentence or symbol to remove line"):
new_f.write(line)
To delete a specific line of a file by its line number:
Replace variables filename and line_to_delete with the name of your file and the line number you want to delete.
filename = 'foo.txt'
line_to_delete = 3
initial_line = 1
file_lines = {}
with open(filename) as f:
content = f.readlines()
for line in content:
file_lines[initial_line] = line.strip()
initial_line += 1
f = open(filename, "w")
for line_number, line_content in file_lines.items():
if line_number != line_to_delete:
f.write('{}\n'.format(line_content))
f.close()
print('Deleted line: {}'.format(line_to_delete))
Example output:
Deleted line: 3
Take the contents of the file, split it by newline into a tuple. Then, access your tuple's line number, join your result tuple, and overwrite to the file.
I'm new to python hence I am unable to implement the solutions I've found online in order to fix my problem.
I am trying to add a specific string to the end of a specific line to a textfile. As I understand text commands, I must overwrite the file if I don't want to append to the end of it. So, my solution is as follows:
ans = 'test'
numdef = ['H',2]
f = open(textfile, 'r')
lines = f.readlines()
f.close()
f = open(textfile, 'w')
f.write('')
f.close()
f = open(textfile, 'a')
for line in lines:
if int(line[0]) == numdef[1]:
if str(line[2]) == numdef[0]:
k = ans+ line
f.write(k)
else:
f.write(line)
Basically, I am trying to add variable ans to the end of a specific line, the line which appears in my list numdef. So, for example, for
2 H: 4,0 : Where to search for information : google
I want
2 H: 4,0 : Where to search for information : google test
I have also tried using line.insert() but to no avail.
I understand using the 'a' function of the open command is not so relevant and helpful here, but I am out of ideas. Would love tips with this code, or if maybe I should scrap it and rethink the whole thing.
Thank you for your time and advice!
When you use the method
lines = f.readlines()
Python automatically adds "\n" to the end of each line.
Try instead of :
k = line+ans
The following:
k = line.rstrip('\n') + ans
Good luck!
Try this. You don't have an else case if it meets the first requirement but not the other.
ans = 'test'
numdef = ['H',2]
f = open(textfile, 'r')
lines = f.readlines()
f.close()
f = open(textfile, 'w')
f.write('')
f.close()
f = open(textfile, 'a')
for line in lines:
if int(line[0]) == numdef[1] and str(line[2]) == numdef[0]:
k = line.replace('\n','')+ans
f.write(k)
else:
f.write(line)
f.close()
Better way:
#initialize variables
ans = 'test'
numdef = ['H',2]
#open file in read mode, add lines into lines
with open(textfile, 'r') as f:
lines=f.readlines()
#open file in write mode, override everything
with open(textfile, 'w') as f:
#in the list comprehension, loop through each line in lines, if both of the conditions are true, then take the line, remove all newlines, and add ans. Otherwise, remove all the newlines and don't add anything. Then combine the list into a string with newlines as separators ('\n'.join), and write this string to the file.
f.write('\n'.join([line.replace('\n','')+ans if int(line[0]) == numdef[1] and str(line[2]) == numdef[0] else line.replace('\n','') for line in lines]))
Let's say I have a text file full of nicknames. How can I delete a specific nickname from this file, using Python?
First, open the file and get all your lines from the file. Then reopen the file in write mode and write your lines back, except for the line you want to delete:
with open("yourfile.txt", "r") as f:
lines = f.readlines()
with open("yourfile.txt", "w") as f:
for line in lines:
if line.strip("\n") != "nickname_to_delete":
f.write(line)
You need to strip("\n") the newline character in the comparison because if your file doesn't end with a newline character the very last line won't either.
Solution to this problem with only a single open:
with open("target.txt", "r+") as f:
d = f.readlines()
f.seek(0)
for i in d:
if i != "line you want to remove...":
f.write(i)
f.truncate()
This solution opens the file in r/w mode ("r+") and makes use of seek to reset the f-pointer then truncate to remove everything after the last write.
The best and fastest option, rather than storing everything in a list and re-opening the file to write it, is in my opinion to re-write the file elsewhere.
with open("yourfile.txt", "r") as file_input:
with open("newfile.txt", "w") as output:
for line in file_input:
if line.strip("\n") != "nickname_to_delete":
output.write(line)
That's it! In one loop and one only you can do the same thing. It will be much faster.
This is a "fork" from #Lother's answer (which I believe that should be considered the right answer).
For a file like this:
$ cat file.txt
1: october rust
2: november rain
3: december snow
This fork from Lother's solution works fine:
#!/usr/bin/python3.4
with open("file.txt","r+") as f:
new_f = f.readlines()
f.seek(0)
for line in new_f:
if "snow" not in line:
f.write(line)
f.truncate()
Improvements:
with open, which discard the usage of f.close()
more clearer if/else for evaluating if string is not present in the current line
The issue with reading lines in first pass and making changes (deleting specific lines) in the second pass is that if you file sizes are huge, you will run out of RAM. Instead, a better approach is to read lines, one by one, and write them into a separate file, eliminating the ones you don't need. I have run this approach with files as big as 12-50 GB, and the RAM usage remains almost constant. Only CPU cycles show processing in progress.
I liked the fileinput approach as explained in this answer:
Deleting a line from a text file (python)
Say for example I have a file which has empty lines in it and I want to remove empty lines, here's how I solved it:
import fileinput
import sys
for line_number, line in enumerate(fileinput.input('file1.txt', inplace=1)):
if len(line) > 1:
sys.stdout.write(line)
Note: The empty lines in my case had length 1
If you use Linux, you can try the following approach.
Suppose you have a text file named animal.txt:
$ cat animal.txt
dog
pig
cat
monkey
elephant
Delete the first line:
>>> import subprocess
>>> subprocess.call(['sed','-i','/.*dog.*/d','animal.txt'])
then
$ cat animal.txt
pig
cat
monkey
elephant
Probably, you already got a correct answer, but here is mine.
Instead of using a list to collect unfiltered data (what readlines() method does), I use two files. One is for hold a main data, and the second is for filtering the data when you delete a specific string. Here is a code:
main_file = open('data_base.txt').read() # your main dataBase file
filter_file = open('filter_base.txt', 'w')
filter_file.write(main_file)
filter_file.close()
main_file = open('data_base.txt', 'w')
for line in open('filter_base'):
if 'your data to delete' not in line: # remove a specific string
main_file.write(line) # put all strings back to your db except deleted
else: pass
main_file.close()
Hope you will find this useful! :)
I think if you read the file into a list, then do the you can iterate over the list to look for the nickname you want to get rid of. You can do it much efficiently without creating additional files, but you'll have to write the result back to the source file.
Here's how I might do this:
import, os, csv # and other imports you need
nicknames_to_delete = ['Nick', 'Stephen', 'Mark']
I'm assuming nicknames.csv contains data like:
Nick
Maria
James
Chris
Mario
Stephen
Isabella
Ahmed
Julia
Mark
...
Then load the file into the list:
nicknames = None
with open("nicknames.csv") as sourceFile:
nicknames = sourceFile.read().splitlines()
Next, iterate over to list to match your inputs to delete:
for nick in nicknames_to_delete:
try:
if nick in nicknames:
nicknames.pop(nicknames.index(nick))
else:
print(nick + " is not found in the file")
except ValueError:
pass
Lastly, write the result back to file:
with open("nicknames.csv", "a") as nicknamesFile:
nicknamesFile.seek(0)
nicknamesFile.truncate()
nicknamesWriter = csv.writer(nicknamesFile)
for name in nicknames:
nicknamesWriter.writeRow([str(name)])
nicknamesFile.close()
In general, you can't; you have to write the whole file again (at least from the point of change to the end).
In some specific cases you can do better than this -
if all your data elements are the same length and in no specific order, and you know the offset of the one you want to get rid of, you could copy the last item over the one to be deleted and truncate the file before the last item;
or you could just overwrite the data chunk with a 'this is bad data, skip it' value or keep a 'this item has been deleted' flag in your saved data elements such that you can mark it deleted without otherwise modifying the file.
This is probably overkill for short documents (anything under 100 KB?).
I like this method using fileinput and the 'inplace' method:
import fileinput
for line in fileinput.input(fname, inplace =1):
line = line.strip()
if not 'UnwantedWord' in line:
print(line)
It's a little less wordy than the other answers and is fast enough for
Save the file lines in a list, then remove of the list the line you want to delete and write the remain lines to a new file
with open("file_name.txt", "r") as f:
lines = f.readlines()
lines.remove("Line you want to delete\n")
with open("new_file.txt", "w") as new_f:
for line in lines:
new_f.write(line)
here's some other method to remove a/some line(s) from a file:
src_file = zzzz.txt
f = open(src_file, "r")
contents = f.readlines()
f.close()
contents.pop(idx) # remove the line item from list, by line number, starts from 0
f = open(src_file, "w")
contents = "".join(contents)
f.write(contents)
f.close()
You can use the re library
Assuming that you are able to load your full txt-file. You then define a list of unwanted nicknames and then substitute them with an empty string "".
# Delete unwanted characters
import re
# Read, then decode for py2 compat.
path_to_file = 'data/nicknames.txt'
text = open(path_to_file, 'rb').read().decode(encoding='utf-8')
# Define unwanted nicknames and substitute them
unwanted_nickname_list = ['SourDough']
text = re.sub("|".join(unwanted_nickname_list), "", text)
Do you want to remove a specific line from file so use this snippet short and simple code you can easily remove any line with sentence or prefix(Symbol).
with open("file_name.txt", "r") as f:
lines = f.readlines()
with open("new_file.txt", "w") as new_f:
for line in lines:
if not line.startswith("write any sentence or symbol to remove line"):
new_f.write(line)
To delete a specific line of a file by its line number:
Replace variables filename and line_to_delete with the name of your file and the line number you want to delete.
filename = 'foo.txt'
line_to_delete = 3
initial_line = 1
file_lines = {}
with open(filename) as f:
content = f.readlines()
for line in content:
file_lines[initial_line] = line.strip()
initial_line += 1
f = open(filename, "w")
for line_number, line_content in file_lines.items():
if line_number != line_to_delete:
f.write('{}\n'.format(line_content))
f.close()
print('Deleted line: {}'.format(line_to_delete))
Example output:
Deleted line: 3
Take the contents of the file, split it by newline into a tuple. Then, access your tuple's line number, join your result tuple, and overwrite to the file.