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Python notes · Topic 1 of 22 · 4 min read

Python introduction: your first program

Python introduction notes for beginners: what Python is, installing it, your first program with print(), sep and end, comments and reading error messages.

What is a program? What is Python?

A program is a list of instructions a computer follows, one after another. Python is a programming language: a way of writing those instructions that is close to plain English.

Python is used by beginners and by large companies alike. It runs websites (Instagram, parts of YouTube), analyses data, trains AI models and automates boring office work. It is popular in schools because the code is short and easy to read.

print("Namaste, Python!")

That one line is a complete Python program. In many other languages the same job needs five or more lines.

Installing Python and an editor

  1. Download Python 3 from python.org and run the installer.
  2. On Windows, tick Add python.exe to PATH on the first screen before you click Install.
  3. Install VS Code as your editor, and add its Python extension.

Check the install by opening Command Prompt and typing python --version. You should see something like Python 3.12.4.

There are two ways to run Python:

WayWhat it isUse it for
Shell (IDLE or python in a terminal)Type one line, see the answer at onceQuick tests, a calculator
Script (a .py file)Write many lines, save, then runReal programs you want to keep

print() displays whatever you put inside the brackets.

print("Hello")          # text must be in quotes
print(25)               # numbers need no quotes
print(10 + 5)           # Python works out the sum first: 15
print("Age:", 16)       # many items, separated by commas

Text in quotes is called a string. You can use single quotes 'Hi' or double quotes "Hi"; both work the same.

sep and end

When you print several items, Python puts a space between them and a new line at the end. You can change both.

print("10", "05", "2026", sep="-")     # 10-05-2026
print("Loading", end="...")
print("done")                          # Loading...done
  • sep sets what goes between items (default: a space).
  • end sets what goes after the last item (default: a new line, \n).

Escape characters

CodeMeaning
\nnew line
\ttab (lines text up in columns)
\"a double quote inside a double-quoted string
print("Name:\tAsha\nClass:\t10")

Comments

A comment starts with #. Python ignores everything after it on that line. Use comments to explain *why* the code does something.

# Calculate the total fee for one student
fee = 1200   # monthly fee in rupees

How Python runs your program

Python reads your file from top to bottom, one line at a time. If line 5 has an error, lines 1 to 4 have already run, and line 6 never runs.

Reading error messages

When something is wrong, Python stops and prints an error. The last line tells you the *type* of error, and the line number tells you *where*.

  File "hello.py", line 2
    print("Hi"
         ^
SyntaxError: '(' was never closed

Three errors every beginner meets

ErrorCauseExample
SyntaxErrorPython cannot understand the line: a missing bracket or quoteprint("Hi"
NameErrorYou used a name Python does not know, often a spelling mistakeprnt("Hi")
IndentationErrorSpaces at the start of a line where none are expected (or missing) print("Hi")

Tip: read the error from the bottom up. The last line says what went wrong; the line number above it says where.

Common mistakes

  • Forgetting quotes around text: print(Hello) gives a NameError, because Python thinks Hello is a variable.
  • Writing Print with a capital P. Python is case-sensitive: print and Print are different names.
  • Using curly “smart quotes” copied from Word or WhatsApp. Python only accepts plain " and '.

Key points

  • A Python program is a text file ending in .py, run from top to bottom.
  • print() shows text and values; sep and end change spacing and line endings.
  • # starts a comment that Python ignores.
  • Read errors from the bottom line up, and check the line number.

Practice questions

1. What does print("A", "B", "C", sep="") show?

ABC. An empty sep means nothing goes between the items.

2. Write one print statement that shows your name and class on two separate lines.
print("Name: Riya\nClass: 9")
3. A student types print("Total" 50). Which error appears, and how do you fix it?

A SyntaxError, because the two items need a comma between them: print("Total", 50).

4. What is the output of these two lines?
print("Good", end=" ")
print("morning")

Good morning on one line, because end=" " replaced the usual new line with a space.

5. Why does prnt("Hello") give a NameError and not a SyntaxError?

The line is grammatically fine, but Python does not know any function called prnt. Unknown names cause a NameError.