Now you're thinking like someone who automates things. Same open() function, different mode. Use "w" for write mode:

with open("output.txt", "w") as file:
    file.write("Hello, world!\n")
    file.write("Second line.\n")

Two critical things about write mode: it creates the file if it doesn't exist, and it overwrites the file completely if it does. Every time you open with "w", you start with a blank slate.

Good instinct. That's why append mode exists — "a":

# First run — creates the file
with open("log.txt", "a") as file:
    file.write("Event 1: Started\n")

# Second run — adds to the file
with open("log.txt", "a") as file:
    file.write("Event 2: Completed\n")

# log.txt now contains both lines

Append mode keeps everything that's already there and tacks new content on the end. Perfect for log files, running totals, or any time you're building up data over time.

Yep — unlike print(), .write() writes exactly what you give it. Nothing more. If you want a newline, include "\n" yourself.

For writing multiple lines, build the full string first and write once:

data = ["Alice,92", "Bob,85", "Charlie,67"]
output = "\n".join(data) + "\n"
with open("students.txt", "w") as file:
    file.write(output)

The "\n".join() pattern — you've been using it since Week 2 with strings. Now it's building file output.

Build each line as a comma-separated string, then write them all:

students = [
    {"name": "Alice", "score": 92, "grade": "A"},
    {"name": "Bob", "score": 85, "grade": "B"},
]

header = "name,score,grade"
lines = [header]
for s in students:
    lines.append(f"{s['name']},{s['score']},{s['grade']}")

with open("report.csv", "w") as file:
    file.write("\n".join(lines) + "\n")

This pattern — build a list of strings, join them, write once — is how you produce any output file. And yes, you could email that CSV to your team and they'd open it in Excel like nothing happened.

Same idea, formatted text instead of raw data:

report_lines = []
report_lines.append("=== Student Report ===")
report_lines.append(f"Total Students: {len(students)}")
report_lines.append(f"Average Score: {avg}")
report_lines.append("")
for s in students:
    report_lines.append(f"  {s['name']}: {s['score']} ({s['grade']})")

with open("report.txt", "w") as file:
    file.write("\n".join(report_lines) + "\n")

That's the pipeline: file in, process, file out. And in the zuzu sandbox, use zuzu.files.write(filename, content):

import zuzu
zuzu.files.write("report.txt", "\n".join(report_lines))

Same pattern. Build your content, write it in one call.

Let's build a real report.