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How to Read and Write CSV, JSON and Text Files in Python (with open and with)

P9.1 File Paths and the Working Folder in Python

By , trainer LinkedIn Last updated:

Why. Most "file not found" errors are path problems. Python looks for files in the current working folder unless you give a full path.

What.

  • Working folder — where Python is running now. os.getcwd() shows it.
  • Relative path — data/sales.csv (from the working folder).
  • Absolute path — the full path, like C:/Users/you/data/sales.csv.
  • pathlib.Path — a modern, safe way to build paths on Windows and Mac.

How.

Find and check a file

  1. Print the working folder.
  2. List files with os.listdir().
  3. Build the path with Path("data") / "sales.csv".
  4. Check it exists with .exists().

Worked example A — Where am I?.

Step 1 — What we do. We check that a file exists before opening it.

Step 2 — Make the input file sales.csv in the same folder as your code:

date,store,item,qty,price
2026-03-01,Pune,Milk,3,56
2026-03-01,Mumbai,Bread,2,40
2026-03-02,Pune,Eggs,1,84
2026-03-02,Nagpur,Milk,5,56

About this data: each line after the first is one sale. The first line is the header: date of sale, store city, item name, qty (units sold) and price (₹ per unit).

Step 3 — Type and run this code.

from pathlib import Path
p = Path("sales.csv")
print(p.exists())
print(p.suffix)

Step 4 — Output you should see.

True
.csv

Step 5 — What it means. exists() is True because the file is in the working folder. .suffix gives the extension.

Worked example B — Build a path safely.

Step 1 — What we do. Paths are joined with / using pathlib; it works on Windows and Mac.

Step 2 — Type and run this code.

from pathlib import Path
p = Path("reports") / "2026" / "march.csv"
print(p.as_posix())
print(p.name, p.stem)

Step 3 — Output you should see.

reports/2026/march.csv
march.csv march

Step 4 — What it means. No worry about \ vs /. .name is the file name and .stem is the name without the extension.

Ravindra Bagale's Tip

On Windows, write paths with forward slashes C:/data/file.csv or use pathlib. Backslashes inside normal strings cause strange bugs.