Python delete line and write over it - python

i have proplem here with my code
i am using for loop to save results in txt file
every time i use it it's saving the last line and delete the old line
here is code:
for i in domains:
requests.get(i)
if req.status_code == 200:
print('[+]:', i + '/')
file = open(save,'w')
file.write(domain)
file.close()
so after run the code it's save the last domain or last results and delete the old results
so i want solution
thanks.


Open the file in append mode:
open(filename,'a')
Your code should be:
for i in domains:
requests.get(i)
if req.status_code == 200:
print('[+]:', i + '/')
file = open(save,'a')
file.write(i)
file.close()


Try open it with a instead of w, so:
file = open(save, 'a')
it should appends to the file instead of writing to it


You sould use 'a' instead of 'w' in "file = open(save,'w')"


The problem here is arising because you are opening the file for writing on every iteration of the loop. Because you are opening the file with mode 'w', the file is being overwritten every time. (See documentation.)
It would be better to open the file once only, outside the loop.
For example:
file = open(save, 'w')
for i in domains:
# do some stuff...
file.write(some_data)
file.close()
You can also use with in conjuction with the open function:
with open(save, 'w') as file:
for i in domains:
# do some stuff...
file.write(some_data)
In this case, there is no need for an explicit call to file.close(). This will be done automatically when the loop ends, or even if something happens inside the with block like an exception being raised (i.e. error occurring) or a return from the function (if applicable).
Be aware that because of output buffering, data written to the file during one iteration might not actually get written to the file until some later iteration or after the file is closed. If this would be a problem, then you can insert a flush call to force a low-level write so that other processes can see the data:
with open(save, 'w') as file:
for i in domains:
# do some stuff...
file.write(some_data)
file.flush()
If there is some reason why you need to open the file inside the loop, then you could open it in append mode using 'a', and the data will be written after the end of the existing file. (Again, see the documentation linked earlier.) For example:
for i in domains:
# do some stuff...
file = open(save, 'a')
file.write(some_data)
file.close()
or again, better like this:
for i in domains:
with open(save, 'a') as file:
# do some stuff...
file.write(some_data)
Be aware that if the output file already exists before the program is started, then the contents of the existing file will remain because you are always opening it in append mode. Depending on your application, this might or might not be desirable.

Related

How can you append and write to the same text file in python 3?

In one of my games, I need to append to the end of the game saves file if I the user is new or change the balance in the file if the user already has a game save. This requires me to open the file separately in write and append modes. Is there a way I could do this sumultaneously?
def write_to_txt(self):
if self.saved_game:
with open("Game Saves.txt", "w") as f:
new_saved_game = self.list_saved_game[0] + self.list_saved_game[1][:10] + str(self.balance) + "\n"
f.write(''.join(self.contents_of_txt_file).replace(self.saved_game, new_saved_game))
else:
with open("Game Saves.txt", "a") as f:
f.write("User: {}\nBalance = {}\n".format(self.name, self.balance))

It seems to me that you want a way to delete the contents of the file while in append mode? You could open it in append mode and then use the .truncate() method when you want to start writing from a clean file (as you would if you opened it in write mode).
See this answer: How to erase the file contents of text file in Python?

You can use something like:
with open("Game Saves.txt", ('a' if self.saved_game else 'w')) as f:
<rest of the code>

Not able to clear file Contents

I have a file which has below data.
edit 48
set dst 192.168.4.0 255.255.255.0
set device "Tague-VPN"
set comment "Yeshtel"
edit 180
set dst 64.219.107.45 255.255.255.255
set device "Austin-Backup"
set comment "images.gsmc.org"
I want to copy the commands under edit only if Set device is Austin-Backup.
string = 'set device'
word = '"Austin-Backup"'
with open('test.txt') as oldfile, open('script.txt', 'w') as newfile:
for line in oldfile:
newfile.write(line)
newfile.write('\n')
if string not in line:
pass
elif string in line:
if word not in line:
a = open('script.txt', 'w')
a.close()
else:
pass
I am trying to write test file content to new file(script) and if command "set comment "Yeshtel"" is found i want to delete contents in new file. I tried to delete but its not happening. I am new to Python, Can you please tell what is the Prob??
I got to know that reopening the same file in Write mode will clear the contents..

I suspect the issue is that you have the same file open twice, once as newfile and a second time as a. While it should be truncated when you open it as a and then close it, the writes you made on newfile may still appear if the filesystem had cached them until after the truncated version was written.
I suggest only opening the file once. When you need to truncate it, call the truncate method on it.
if word not in line:
newfile.truncate()
If you might write more to the file after truncating, you should probably also seek back to the start position (e.g. newfile.seek(0)). If you're going to be done with the file after truncating it, that step is not needed.

Should be something like this
temp_lines = []
last_line_was_edit = False
found_keyword = False
keyword = "Austin-Backup"
with open('test.txt') as oldfile, open('script.txt', 'w') as newfile:
for line in oldfile:
if last_line_was_edit and temp_lines:
if found_keyword:
newfile.writelines(temp_lines)
temp_lines = []
if line.startswith("edit"):
last_line_was_edit = True
else:
if keyword in line:
found_keyword = True
temp_lines.append(line)
Please note that you should not open the file twice. Just use an temporary variable and write only what have to be written

Delete a file after reading

In my code, user uploads file which is saved on server and read using the server path. I'm trying to delete the file from that path after I'm done reading it. But it gives me following error instead:
An error occurred while reading file. [WinError 32] The process cannot access the file because it is being used by another process
I'm reading file using with, and I've tried f.close() and also f.closed but its the same error every time.
This is my code:
f = open(filePath)
with f:
line = f.readline().strip()
tempLst = line.split(fileSeparator)
if(len(lstHeader) != len(tempLst)):
headerErrorMsg = "invalid headers"
hjsonObj["Line No."] = 1
hjsonObj["Error Detail"] = headerErrorMsg
data['lstErrorData'].append(hjsonObj)
data["status"] = True
f.closed
return data
f.closed
after this code I call the remove function:
os.remove(filePath)
Edit: using with open(filePath) as f: and then trying to remove the file gives the same error.

Instead of:
f.closed
You need to say:
f.close()
closed is just a boolean property on the file object to indicate if the file is actually closed.
close() is method on the file object that actually closes the file.
Side note: attempting a file delete after closing a file handle is not 100% reliable. The file might still be getting scanned by the virus scanner or indexer. Or some other system hook is holding on to the file reference, etc... If the delete fails, wait a second and try again.

Use below code:
import os
os.startfile('your_file.py')
To delete after completion:
os.remove('your_file.py')

This
import os
path = 'path/to/file'
with open(path) as f:
for l in f:
print l,
os.remove(path)
should work, with statement will automatically close the file after the nested block of code
if it fails, File could be in use by some external factor. you can use Redo pattern.
while True:
try:
os.remove(path)
break
except:
time.sleep(1)

There is probably an application that is opening the file; check and close the application before executing your code:
os.remove(file_path)
Delete files that are not used by another application.

Python file handling and lines input

If i have a python file let's say abc.txt and contains the following data ONLY
#data(data may change dynamically)
#data(data may change dynamically)
I want to delete the file itself. (abc.txt)
But what if there's a python file which is still the same file containing the data AND something else, I will want to keep the file. (abc.txt)
#12345 (Number may change dynamically)
#46346346 (Number may change dynamically)
DATA
DATA
DATA
Is there anyway i can do this? Sorry I am really new to python and I can't figure out a way to delete the file itself because of the ever-changing conditions.

This code works:
import os
def remove_file(filename):
with open(filename, 'r') as f:
for line in f:
line = line.strip()
if line and not line.startswith('#'):
return False
os.remove(filename)
return True
if __name__ == '__main__':
if remove_file('abc.txt'):
print 'File was removed!'
else:
print 'File was not removed!'

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

I am getting an interesting error while trying to use Unpickler.load(), here is the source code:
open(target, 'a').close()
scores = {};
with open(target, "rb") as file:
unpickler = pickle.Unpickler(file);
scores = unpickler.load();
if not isinstance(scores, dict):
scores = {};
Here is the traceback:
Traceback (most recent call last):
File "G:\python\pendu\user_test.py", line 3, in <module>:
save_user_points("Magix", 30);
File "G:\python\pendu\user.py", line 22, in save_user_points:
scores = unpickler.load();
EOFError: Ran out of input
The file I am trying to read is empty.
How can I avoid getting this error, and get an empty variable instead?

Most of the answers here have dealt with how to mange EOFError exceptions, which is really handy if you're unsure about whether the pickled object is empty or not.
However, if you're surprised that the pickle file is empty, it could be because you opened the filename through 'wb' or some other mode that could have over-written the file.
for example:
filename = 'cd.pkl'
with open(filename, 'wb') as f:
classification_dict = pickle.load(f)
This will over-write the pickled file. You might have done this by mistake before using:
...
open(filename, 'rb') as f:
And then got the EOFError because the previous block of code over-wrote the cd.pkl file.
When working in Jupyter, or in the console (Spyder) I usually write a wrapper over the reading/writing code, and call the wrapper subsequently. This avoids common read-write mistakes, and saves a bit of time if you're going to be reading the same file multiple times through your travails

I would check that the file is not empty first:
import os
scores = {} # scores is an empty dict already
if os.path.getsize(target) > 0:
with open(target, "rb") as f:
unpickler = pickle.Unpickler(f)
# if file is not empty scores will be equal
# to the value unpickled
scores = unpickler.load()
Also open(target, 'a').close() is doing nothing in your code and you don't need to use ;.

It is very likely that the pickled file is empty.
It is surprisingly easy to overwrite a pickle file if you're copying and pasting code.
For example the following writes a pickle file:
pickle.dump(df,open('df.p','wb'))
And if you copied this code to reopen it, but forgot to change 'wb' to 'rb' then you would overwrite the file:
df=pickle.load(open('df.p','wb'))
The correct syntax is
df=pickle.load(open('df.p','rb'))

As you see, that's actually a natural error ..
A typical construct for reading from an Unpickler object would be like this ..
try:
data = unpickler.load()
except EOFError:
data = list() # or whatever you want
EOFError is simply raised, because it was reading an empty file, it just meant End of File ..

You can catch that exception and return whatever you want from there.
open(target, 'a').close()
scores = {};
try:
with open(target, "rb") as file:
unpickler = pickle.Unpickler(file);
scores = unpickler.load();
if not isinstance(scores, dict):
scores = {};
except EOFError:
return {}

if path.exists(Score_file):
try :
with open(Score_file , "rb") as prev_Scr:
return Unpickler(prev_Scr).load()
except EOFError :
return dict()

Had the same issue. It turns out when I was writing to my pickle file I had not used the file.close(). Inserted that line in and the error was no more.

I have encountered this error many times and it always occurs because after writing into the file, I didn't close it. If we don't close the file the content stays in the buffer and the file stays empty.
To save the content into the file, either file should be closed or file_object should go out of scope.
That's why at the time of loading it's giving the ran out of input error because the file is empty. So you have two options :
file_object.close()
file_object.flush(): if you don't wanna close your file in between the program, you can use the flush() function as it will forcefully move the content from the buffer to the file.

This error comes when your pickle file is empty (0 Bytes). You need to check the size of your pickle file first. This was the scenario in my case. Hope this helps!

Note that the mode of opening files is 'a' or some other have alphabet 'a' will also make error because of the overwritting.
pointer = open('makeaafile.txt', 'ab+')
tes = pickle.load(pointer, encoding='utf-8')

temp_model = os.path.join(models_dir, train_type + '_' + part + '_' + str(pc))
# print(type(temp_model)) # <class 'str'>
filehandler = open(temp_model, "rb")
# print(type(filehandler)) # <class '_io.BufferedReader'>
try:
pdm_temp = pickle.load(filehandler)
except UnicodeDecodeError:
pdm_temp = pickle.load(filehandler, fix_imports=True, encoding="latin1")

from os.path import getsize as size
from pickle import *
if size(target)>0:
with open(target,'rb') as f:
scores={i:j for i,j in enumerate(load(f))}
else: scores={}
#line 1.
we importing Function 'getsize' from Library 'OS' sublibrary 'path' and we rename it with command 'as' for shorter style of writing. Important is hier that we loading only one single Func that we need and not whole Library!
line 2.
Same Idea, but when we dont know wich modul we will use in code at the begining, we can import all library using a command '*'.
line 3.
Conditional Statement... if size of your file >0 ( means obj is not an empty). 'target' is variable that schould be a bit earlier predefined.
just an Example : target=(r'd:\dir1\dir.2..\YourDataFile.bin')
Line 4.
'With open(target) as file:' an open construction for any file, u dont need then to use file.close(). it helps to avoid some typical Errors such as "Run out of input" or Permissions rights.
'rb' mod means 'rea binary' that u can only read(load) the data from your binary file but u cant modify/rewrite it.
Line5.
List comprehension method in applying to a Dictionary..
line 6. Case your datafile is empty, it will not raise an any Error msg, but return just an empty dictionary.

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