Code se haath daalna

Wahi teen verbs Python mein — plus ek superpower jo shell ke paas nahi.

SENSEX extraction koi chalaak shell one-liner nahi thi — wo ek Python script thi jo 17 archives mein haath daal rahi thi. Code mein aapko wahi list → stream-one → bulk verbs milte hain, par ek move bhi milta hai jo command line nahi kar sakti: ek archive ko memory mein rakho aur reader ko ek seekable buffer de do. Yahi ek trick wajah hai ki ek zip-ke-andar-zip ko koi temp file nahi chahiye thi.

Wahi teen verbs, Python mein

Standard library L1 ko bilkul mirror karti hai. Key farak: read() aapko bytes in memory deta hai, disk par file nahi.1

import zipfile, io

# open once; the central directory is read for you
with zipfile.ZipFile("data.zip") as z:
    names = z.namelist()                 # LIST — names from the index

    data  = z.read("SENSEX.csv")         # STREAM ONE — bytes, in RAM (no file written)
    text  = data.decode()                # bytes → str when you need text

    with z.open("SENSEX.csv") as f:      # or a file-like stream, line by line
        for line in io.TextIOWrapper(f):
            process(line)

    z.extractall("out/")                 # BULK — write everything to disk

Superpower: memory mein ek seekable buffer

Lesson 2 ka rule yaad karo: ek zip reader ko seek karna padta hai, aur ek pipe nahi kar sakti. Par seekable ka matlab disk par hona zaroori nahi — RAM bhi seekable ho sakti hai. io.BytesIO bytes ke ek bunch ko ek file-like object mein lapet deta hai jo seek() support karta hai.2 Toh aap ek aisi zip khol sakte ho jo sirf memory mein hai — jaise, ek jo aapne abhi doosri zip se nikaali.

with zipfile.ZipFile(outer_path) as oz:                  # outer zip on disk
    inner_bytes = oz.read("BSE_IDX_1MIN_20250203.zip")  # inner zip → bytes in RAM
    with zipfile.ZipFile(io.BytesIO(inner_bytes)) as iz:  # RAM buffer IS seekable
        csv = iz.read("SENSEX.csv")                     # reach into the inner zip — done

Code mein tar: streaming, file-like members

tarfile L2 ko mirror karta hai. Kyunki tar ek streaming format hai, extractfile() aapko ek file-like stream deta hai jise sequentially padho — random access nahi.3

import tarfile

with tarfile.open("data.tar.gz") as t:     # compression auto-detected
    names = t.getnames()                   # LIST — walks the archive
    f = t.extractfile("dir/SENSEX.csv")    # STREAM ONE — a file-like object
    data = f.read()                        # read its bytes

Code bhi kahaan temp file nahi bacha sakta

In-memory buffer ek superpower hai jiska ek hard edge hai. Wo isliye kaam karta hai kyunki zipfile/tarfile ek file object accept karte hain. Par jab reader ek alag program ho — jaise unrar, subprocess se call kiya gaya — wo aapki Python memory dekh nahi sakta; use disk par ek real path chahiye. Wahaan koi BytesIO aapko nahi bachayega.

Yahi poori logic hai SENSEX script ke teen handlers ke peeche:

Toh heuristic: in-process libraries ek seekable buffer lete hain; out-of-process tools ek path lete hain. BytesIO uthao jab koi Python library padhegi; temp file uthao jab aapko shell out karna pade.

Recall check

Retrieve karo, dobara mat padho. Memory se jawaab do; feedback turant.

Sources

1. Python Standard Library — zipfile. ZipFile.namelist(), read() (bytes lautata hai), open() (file-like), extractall(); ek path ya ek file object accept karta hai.
2. Python Standard Library — io.BytesIO. Ek in-memory binary stream poore seek()/read() ke saath — ek seekable file jo disk ko kabhi nahi chuti.
3. Python Standard Library — tarfile. open() (gzip/bz2/xz auto-detect), getnames(), extractfile() (file-like, sequential).