Python skip last line file

How to remove last N lines from txt file with Python?

assuming by 3rd line, he means human style counting rather than zeroth-indexed) (Note that the with line returns a file object which will be automatically closed even if for example the length of myfile is less than 3; this file object also provides an iterator which then gets converted into a straight list so you can pick a specific line.) The file is huge in size,so to remove first few line I’m using the following code Solution 1: Here’s a generalized generator for truncating any iterable: Using , you can do this: Solution 2: If every line has a different length, and you can’t predict when to stop with the file size, your python script has no way to know.

How to remove last N lines from txt file with Python?

I would like to know what is the fastest and more efficient way of deleting last N lines of a .txt file.

I have been looking for different previous questions and I found that reading and copying lines again is one way.

Remove lines from textfile with python

Nonetheless, I have been trying to look for other way such as skiprows or skipfooter on pandas and be able to save the outcome to other txt.

At the same time, I have seen threads about «head» and «sed» but not sure about their usage in Python.

Could you, please, give advice on this topic?

if you want to skip last n lines using pandas then:

import pandas as pd df = pd.read_csv('yourfile.txt', skipfooter = N) df.to_csv('yournewfile.txt') 

Change the delimiter using sep = . if necessary

Alternatively do as per the answer you cited, but using with open(..) as good practice:

with open('yourfile.txt') as f1: lines = f1.readlines() with open('yournewfile.txt', 'w') as f2: f2.writelines(lines[:-N]) 

Python — Remove lines from a textfile?, How to remove last N lines from txt file with Python? 0. delete all rows up to a specific row. 0. Removing lines from a file using python . 1. remove first 4 lines in multiple csv files python. 2. Python code to delete headers from txt files. 1. Python — reading and deleting the top line of a file without loading it into …

Python remove last line of a file [duplicate]

I have some files like this:

and I just need to keep the a. values lines. What is the fastest way to remove that last line (which always starts with count = ) ?

You can try this solution:

lines = file.readlines() lines = lines[:-1] 

After opening your file in python as reading mode you could do that for deleting your last line.

You could use readlines() function and apply the slice like

 lines = yourfile.readlines() lines = lines[:-1] 

Many other methods could be found here

List — python file how to delete the last line, Basically, if you want to delete Last line from file using .truncate () you can just save previous position before retrieving next line and call .truncate () with this position after you reach end of file:

Python: How to replace the last word of a line from a text file?

How would I go about replacing the last word of a specific line from all the lines of a text file that has been loaded into Python? I know that if I wanted to access it as a list I’d use [-1] for the specific line, but I don’t know how to do it as a string. An example of the text file is:

A I'm at the shop with Bill. B I'm at the shop with Sarah. C I'm at the shop with nobody. D I'm at the shop with Cameron. 

If you want a more powerful editing option, Regex is your friend.

import re pattern = re.compile(r'\w*(\W*)$') # Matches the last word, and captures any remaining non-word characters # so we don't lose punctuation. This will includes newline chars. line_num = 2 # The line number we want to operate on. new_name = 'Steve' # Who are we at the shops with? Not Allan. with open('shopping_friends.txt') as f: lines = f.readlines() lines[line_num] = re.sub(pattern, new_name + r'\1', lines[line_num]) # substitue the last word for your friend's name, keeping punctuation after it. # Now do something with your modified data here 

please check this , is not 100% pythonic, is more for an overview

file_text = '''I'm at the shop with Bill. I'm at the shop with Sarah. I'm at the shop with nobody. I'm at the shop with Cameron. I'm at the shop with nobody.''' def rep_last_word_line(textin, search_for, replace_with, line_nr): if (isinstance(textin,str)): textin = textin.splitlines() else: # remove enline from all lines - just in case textin = [ln.replace('\n', ' ').replace('\r', '') for ln in textin] if (textin[line_nr] != None): line = textin[line_nr].replace('\n', ' ').replace('\r', '') splited_line = line.split() last_word = splited_line[-1] if (last_word[0:len(search_for)] == search_for): splited_line[-1] = last_word.replace(search_for,replace_with) textin[line_nr] = ' '.join(splited_line) return '\r\n'.join(textin) print rep_last_word_line(file_text,'nobody','Steve',2) print '='*80 print rep_last_word_line(file_text,'nobody','Steve',4) print '='*80 # read content from file f = open('in.txt','r') # file_text = f.read().splitlines() # read text and then use str.splitlines to split line withoud endline character file_text = f.readlines() # this will keep the endline character print rep_last_word_line(file_text,'nobody','Steve',2) 

If you have blank lines, you might want to try splitlines()

lines = your_text.splitlines() lastword = lines[line_to_replace].split()[-1] lines[line_to_replace] = lines[line_to_replace].replace(lastword, word_to_replace_with) 

keep in mind that your changes are in lines now and not your_text so if you want your changes to persist, you’ll have to write out lines instead

with open('shops.txt', 'w') as s: for l in lines: s.write(l) 

Assuming you have a file «example.txt»:

with open("example.txt") as myfile: mylines = list(myfile) lastword = mylines[2].split()[-1] mylines[2] = mylines[2].replace(lastword,"Steve.") 

(Edit: fixed off by one error. assuming by 3rd line, he means human style counting rather than zeroth-indexed)

(Note that the with line returns a file object which will be automatically closed even if for example the length of myfile is less than 3; this file object also provides an iterator which then gets converted into a straight list so you can pick a specific line.)

Python — Don’t write final new line character to a file, Write the newline of each line at the beginning of the next line. To avoid writing a newline at the beginning of the first line, use a variable that is initialized to an empty string and then set to a newline in the loop. import re with open (‘input.txt’) as source, open (‘output.txt’, ‘w’) as target: newline = » for line in …

Skip last 5 line in a file using python

I wanted to remove last few lines in a file using python. The file is huge in size,so to remove first few line I’m using the following code

import sys with open(sys.argv[1],"rb") as f: for _ in range(6):#skip first 6 lines next(f) for line in f: print line 

Here’s a generalized generator for truncating any iterable:

from collections import deque def truncate(iterable, num): buffer = deque(maxlen=num) iterator = iter(iterable) # Initialize buffer for n in range(num): buffer.append(next(iterator)) for item in iterator: yield buffer.popleft() buffer.append(item) truncated_range20 = truncate(range(20), 5) print(list(truncated_range20)) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14] 

Using truncate , you can do this:

from __future__ import print_function import sys from itertools import islice filepath = sys.argv[1] with open(filepath, 'rb') as f: for line in truncate(islice(f, 6, None), 5): print(line, end='') 

If every line has a different length, and you can’t predict when to stop with the file size, your python script has no way to know.

So you need to do some buffering. The easier way is to buffer the whole file, split everything in lines, and then remove that last 5, but you seem to say that you can’t, because the file is huge.

So why not keep only the 5 last lines in memory?

import sys with open(sys.argv[1],"rb") as f: # Skip 6 lines for _ in range(6): next(f) # Create a list that will contain at most 5 lines. # Using a list is not super efficient here (a Queue would be better), but it's only 5 items so. last_lines = [] for line in f: # if the buffer is full, print the first one and remove it from the list. if len(last_lines) == 5: print last_lines.pop(0) # append current line to the list. last_lines.append(line) # when we reach this comment, the last 5 lines will remain on the list. # so you can just drop them. 

As a side note, i suppose that you explicitely said that you want to use python, because you want to replace the «print line» with something else later, or do some additional processing.

If you are not, use your operating system «head» and «tail» commands (i have no idea how they are named on windows though), which will be much more faster (because they use better data structures, read and process big blocks at once, scan the file from the end, are not coded using python, etc).

The following works nicely, and would be suitable for very large files.

It opens the file for updating, skips to almost the end and reads the remaining portion as lines. It then moves the file pointer back to where it started reading from. It then writes back all but the last 5 lines to the file, and truncates the remaining part of the file:

import os back_up = 5 * 200 # Go back from the end more than 5 lines worth with open("foo.txt", "r+") as f: f.seek(-back_up, os.SEEK_END) lines = f.readlines()[:-5] f.seek(-back_up, os.SEEK_END) f.write("".join(lines)) f.truncate() 

You must decide how long you feel each line could roughly be. It does not need to be an exact value, just enough to ensure you have the last lines.

For example if your lines are very long, you could back_up a much larger value, e.g. 10 * 10000 to be on the safe side. This would avoid you having to process the whole of your large file.

Delete blank/empty lines in text file for Python, If you want to remove blank lines from an existing file without writing to a new one, you can open the same file again in read-write mode (denoted by ‘r+’) for writing. Truncate the file at the write position after the writing is done:

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Remove the last line from the text file in Python

In this tutorial, you will learn about how to remove the last line from a text file in Python. Handling files in python play a crucial role in web applications.

Here we use some predefined file handling operations like creating, writing, reading, deleting files. We use these file handling operations to remove the last line from a text file in Python. Hence the first line of our script is as follows:

Open() method:

Using the open() method file operation we open an existing file using Python.

#opening the file.txt fd=open("file.txt","r")# opening the file for reading s=fd.read() #reading the contents of that file to sd fd.close() #closing the file

In the above program, In the first line of the script, we open the file.txt using open() method in reading format and we store the contents of the file in an fd object variable. In the second line, we store the contents of the fd object as the scriptable form in s and finally, we close the file using the close() method.
Note: In file handling operations closing the file is mandatory.

Write() method:

Using the write() method we write the contents in the file. write() method append the specified contents into the existing file.

#writing the file.txt f=open("file.txt","w") # opening the file for writing f.write("rebel") #writing the content into that file f.close() #closing the file

In the above program, In the first line of the script, we open the file.txt using open() method in writing format.
In the second step, using the write() method we have written the contents into that file and closed the file.

Example : Remove the last line from the text file in Python

#remove last line from a text line in python fd=open("file.txt","r") d=fd.read() fd.close() m=d.split("\n") s="\n".join(m[:-1]) fd=open("file.txt","w+") for i in range(len(s)): fd.write(s[i]) fd.close()

Explanation:

• In the first step of our script, we opened the file in reading format and stored its contents in the sd variable using the read() method and closed the file using the close() method.
• In the second step of our script, Using join() and split() methods we had removed the last line from a text file and stored its contents in variable s.
• As the third step of our script, we opened the same file again to rewrite the modified contents into the same file.
• As the last step of our script, Using the write() method we rewritten the modified contents to the file.

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