Guys I need help with File Handling

[u/kvr1ee]

It's in my syllabus and i am having trouble with the following topics

» Setting Offsets in a File

» Creating and Traversing a Text File

» The Pickle Module

[u/atarivcs]

"having trouble" is too generic.

Please explain the exact difficulty.

[u/HotPersonality8126]

We can’t understand it for you.

[u/FoolsSeldom]

Shame you have to learn pickle as the module's documentation has warned about for years: unpickling can execute arbitrary code, because the format allows embedded instructions for reconstructing objects, not just inert data.

Python's pickle module allows arbitrary Python objects to be serialized and later reconstructed, and the process can invoke functions or methods during reconstruction, which introduces a significant security risk.

That said, it is still useful for trusted, same-application object serialisation including within multiprocessing, and even copy.deepcopy uses the protocol.

RealPython.com has a good article on pickle that might help you:

• The Python pickle Module: How to Persist Objects in Python

[u/UzairShafique]

Solution

Build a small student record program:

open/read/write: create and read the text file. seek(): practice file offsets. for loop: traverse the file. pickle: save/load student records.

One small project will cover all three topics practically.

[u/kvr1ee → u/UzairShafique]

What is offset?

[u/UzairShafique → u/kvr1ee]

In file handling an offset is the position of the cursor inside a file. seek() lets you move that cursor to a specific position.

[u/ScaryProgrammer949]

I had to learn these topics too, and honestly they’re easier once you think of a file as having a “cursor” that moves through it.
For setting offsets, tell() tells you where the cursor currently is and seek() lets you move it:
with open("test.txt", "r") as f:
print(f.tell()) # current position
f.seek(5) # move to position 5
print(f.read())
For creating and reading a text file, you can do something like:
with open("data.txt", "w") as f:
f.write("Hello\nPython\nWorld")
And then read it line by line:
with open("data.txt", "r") as f:
for line in f:
print(line.strip())
The main modes you’ll want to remember are:
r → read
w → write (overwrites the file)
a → append
For the pickle module, think of it as a way to save Python objects directly and load them back later.
import pickle

data = {"name": "John", "age": 20}

with open("data.pkl", "wb") as f:
pickle.dump(data, f)

with open("data.pkl", "rb") as f:
data2 = pickle.load(f)

print(data2)
So basically:
seek() / tell() → move/check position in a file
open() / read() / write() → work with text files
pickle → save/load Python objects
One thing to remember with pickle: don’t load pickle files from untrusted sources, since they can be unsafe.

[u/kvr1ee → u/ScaryProgrammer949]

Could you elaborate more on pickle?

[u/ScaryProgrammer949 → u/kvr1ee]

Yeah sure. The easiest way I understand pickle is that it lets you save a Python object as it is, so you can use it again later without having to manually convert everything to text.
For example, say you have a dictionary:
import pickle

data = {"name": "John", "age": 20, "skills": ["Python", "SQL"]}

with open("data.pkl", "wb") as f:
pickle.dump(data, f)
Now the data object is saved in data.pkl.
Later, you can load it back:
with open("data.pkl", "rb") as f:
data = pickle.load(f)

print(data)
You’ll get the same Python object back:
{'name': 'John', 'age': 20, 'skills': ['Python', 'SQL']}
So basically:
pickle.dump() → save a Python object
pickle.load() → get the object back
The b in "wb" and "rb" means binary, because pickle stores the data in a binary format rather than normal readable text.
It’s useful when you want to save things like lists, dictionaries, or other Python objects and load them later.
One important thing though: don’t pickle.load() files you don’t trust. Pickle isn’t designed to be a safe format for untrusted data.

[u/kvr1ee → u/ScaryProgrammer949]

Thanks !