File Handling
open(filename, mode) file kholta hai — modes: "r" (read), "w" (write, overwrite), "a" (append), "r+" (read+write). File object se .read() (poora content), .readline() (ek line), .readlines() (saari lines, list mein) call kar sakte ho.
.write(text) file mein likhta hai. Kaam khatam hone ke baad .close() call karna zaroori hai — warna changes disk par properly save nahi ho sakte (buffering ki wajah se).
# Likhna:
f = open("data.txt", "w")
f.write("Hello, Python!\n")
f.write("Second line\n")
f.close()
# Padhna:
f = open("data.txt", "r")
content = f.read() # poora content ek string mein
print(content)
f.close()
# Line by line:
f = open("data.txt", "r")
for line in f: # file khud iterable hai!
print(line.strip()) # strip() se trailing \n hataao
f.close()- open(filename, mode) — "r"/"w"/"a" modes
- .read()/.readline()/.readlines() — padhne ke tareeke
- .close() zaroori hai — warna changes properly save nahi honge
csv module (Python standard library) CSV files ko easily read/write karne deta hai — manually comma-splitting karne se zyada robust (edge cases jaise commas-inside-quotes handle karta hai).
import csv
with open("students.csv", "w", newline="") as f:
writer = csv.writer(f)
writer.writerow(["name", "marks"])
writer.writerow(["Aarav", 85])
writer.writerow(["Riya", 92])
with open("students.csv", "r") as f:
reader = csv.reader(f)
for row in reader:
print(row) # ['name', 'marks'], ['Aarav', '85'], ...json module Python objects (dicts, lists) ko JSON string mein convert karta hai (json.dumps()) aur wapas (json.loads()) — APIs, config files, data storage mein bahut common.
import json
data = {"name": "Aarav", "age": 20, "skills": ["Python", "SQL"]}
with open("data.json", "w") as f:
json.dump(data, f) # Python object → JSON file
with open("data.json", "r") as f:
loaded = json.load(f) # JSON file → Python object
print(loaded["name"]) # "Aarav"