Is there a way to delete created variables, functions, etc from the memory of the interpreter?

Michael Zippo

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I"ve been searching for the accurate answer to this question for a couple of days now but haven"t got anything good. I"m not a complete beginner in programming, but not yet even on the intermediate level.

When I"m in the shell of Python, I type: dir() and I can see all the names of all the objects in the current scope (main block), there are 6 of them:

["__builtins__", "__doc__", "__loader__", "__name__", "__package__", "__spec__"]

Then, when I"m declaring a variable, for example x = 10, it automatically adds to that lists of objects under built-in module dir(), and when I type dir() again, it shows now:

["__builtins__", "__doc__", "__loader__", "__name__", "__package__", "__spec__", "x"]

The same goes for functions, classes and so on.

How do I delete all those new objects without erasing the standard 6 which where available at the beginning?

I"ve read here about "memory cleaning", "cleaning of the console", which erases all the text from the command prompt window:

>>> import sys
>>> clear = lambda: os.system("cls")
>>> clear()

But all this has nothing to do with what I"m trying to achieve, it doesn"t clean out all used objects.

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Is there a way to delete created variables, functions, etc from the memory of the interpreter? del: Questions

__del__

How can I make a time delay in Python?

5 answers

I would like to know how to put a time delay in a Python script.

2973

Answer #1

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

2973

Answer #2

You can use the sleep() function in the time module. It can take a float argument for sub-second resolution.

from time import sleep
sleep(0.1) # Time in seconds

Is there a way to delete created variables, functions, etc from the memory of the interpreter? del: Questions

__del__

How to delete a file or folder in Python?

5 answers

How do I delete a file or folder in Python?

2639

Answer #1

os.remove() removes a file.
os.rmdir() removes an empty directory.
shutil.rmtree() deletes a directory and all its contents.

Path objects from the Python 3.4+ pathlib module also expose these instance methods:

pathlib.Path.unlink() removes a file or symbolic link.
pathlib.Path.rmdir() removes an empty directory.

2639

Answer #2

os.remove() removes a file.
os.rmdir() removes an empty directory.
shutil.rmtree() deletes a directory and all its contents.

Path objects from the Python 3.4+ pathlib module also expose these instance methods:

pathlib.Path.unlink() removes a file or symbolic link.
pathlib.Path.rmdir() removes an empty directory.

2639

Answer #3

Python syntax to delete a file

import os
os.remove("/tmp/<file_name>.txt")

import os
os.unlink("/tmp/<file_name>.txt")

pathlib Library for Python version >= 3.4

file_to_rem = pathlib.Path("/tmp/<file_name>.txt")
file_to_rem.unlink()

Path.unlink(missing_ok=False)

Unlink method used to remove the file or the symbolik link.

If missing_ok is false (the default), FileNotFoundError is raised if the path does not exist.
If missing_ok is true, FileNotFoundError exceptions will be ignored (same behavior as the POSIX rm -f command).
Changed in version 3.8: The missing_ok parameter was added.

Best practice

First, check whether the file or folder exists or not then only delete that file. This can be achieved in two ways :
a. os.path.isfile("/path/to/file")
b. Use exception handling.

EXAMPLE for os.path.isfile

#!/usr/bin/python
import os
myfile="/tmp/foo.txt"

## If file exists, delete it ##
if os.path.isfile(myfile):
    os.remove(myfile)
else:    ## Show an error ##
    print("Error: %s file not found" % myfile)

Exception Handling

#!/usr/bin/python
import os

## Get input ##
myfile= raw_input("Enter file name to delete: ")

## Try to delete the file ##
try:
    os.remove(myfile)
except OSError as e:  ## if failed, report it back to the user ##
    print ("Error: %s - %s." % (e.filename, e.strerror))

RESPECTIVE OUTPUT

Enter file name to delete : demo.txt
Error: demo.txt - No such file or directory.

Enter file name to delete : rrr.txt
Error: rrr.txt - Operation not permitted.

Enter file name to delete : foo.txt

Python syntax to delete a folder

shutil.rmtree()

Example for shutil.rmtree()

#!/usr/bin/python
import os
import sys
import shutil

# Get directory name
mydir= raw_input("Enter directory name: ")

## Try to remove tree; if failed show an error using try...except on screen
try:
    shutil.rmtree(mydir)
except OSError as e:
    print ("Error: %s - %s." % (e.filename, e.strerror))

__delete__

Is there a simple way to delete a list element by value?

5 answers

I want to remove a value from a list if it exists in the list (which it may not).

a = [1, 2, 3, 4]
b = a.index(6)

del a[b]
print(a)

The above case (in which it does not exist) shows the following error:

Traceback (most recent call last):
  File "D:zjm_codea.py", line 6, in <module>
    b = a.index(6)
ValueError: list.index(x): x not in list

So I have to do this:

a = [1, 2, 3, 4]

try:
    b = a.index(6)
    del a[b]
except:
    pass

print(a)

But is there not a simpler way to do this?

1055

Answer #1

To remove an element"s first occurrence in a list, simply use list.remove:

>>> a = ["a", "b", "c", "d"]
>>> a.remove("b")
>>> print(a)
["a", "c", "d"]

Mind that it does not remove all occurrences of your element. Use a list comprehension for that.

>>> a = [10, 20, 30, 40, 20, 30, 40, 20, 70, 20]
>>> a = [x for x in a if x != 20]
>>> print(a)
[10, 30, 40, 30, 40, 70]

We hope this article has helped you to resolve the problem. Apart from Is there a way to delete created variables, functions, etc from the memory of the interpreter?, check other __del__-related topics.

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Javier Wu

Massachussetts | 2023-03-29

Python functions is always a bit confusing 😭 Is there a way to delete created variables, functions, etc from the memory of the interpreter? is not the only problem I encountered. Will use it in my bachelor thesis

Cornwall Richtgofen

Tallinn | 2023-03-29

Maybe there are another answers? What Is there a way to delete created variables, functions, etc from the memory of the interpreter? exactly means?. Will use it in my bachelor thesis

Boris Richtgofen

Milan | 2023-03-29

COM PHP module is always a bit confusing 😭 Is there a way to delete created variables, functions, etc from the memory of the interpreter? is not the only problem I encountered. Will get back tomorrow with feedback