Python syntax

Programming works only if the computer understands the structure of your code.
This structure is called syntax.

Syntax defines:

• how code must be written

• where spaces matter

• how blocks of code are organised

Even small syntax mistakes can prevent code from running. Clear syntax is not only about avoiding errors. It also makes your code easier for others to read and reuse.

1. Identifiers and case¶

An identifier is a name used for:

• variables

• functions

• classes

Example:

x = 5
X = "Harry"

print(x)
print(X)

Python is case sensitive.

x and X are two different identifiers.

value = 10
Value = 20
print(value)

2. Comments¶

Comments explain your code to humans.
They are ignored by Python.

Comments start with #.

# This is a comment
number = 5  # This comment is after code

print(number)

Good comments:

• explain why something is done

• do not repeat obvious code

3. Strings and quotes¶

Strings represent text.

Python allows:

• single quotes 'text'

• double quotes "text"

• triple quotes """multi-line text"""

The same quote type must start and end the string.

a = 'Eier'
b = "Kuchen"
c = """This is
a multi-line
string"""

print(a, b)
print(c)

Triple quotes are useful for multi line text.

4. Statements and lines¶

Each line in Python normally represents one statement.

x = 5
y = 12

You can write multiple statements on one line using ;, but this reduces readability.

x = 5; y = 12
print(x + y)

In this course, prefer one statement per line.

Continuing long lines¶

Sometimes a statement is too long to fit comfortably on one line.

Inside brackets (), [], or {}, Python automatically allows the statement to continue across multiple lines.

week_days = (
    "Monday",
    "Tuesday",
    "Wednesday",
    "Thursday",
    "Friday"
)

print(week_days)

5. Indentation and blocks¶

Indentation is not just formatting in Python.
It defines structure.

Blocks such as loops, conditions, and functions:

• end with a colon :

• require indentation

Example:

for i in range(0, 10, 2):
    print(i)

If indentation is missing or inconsistent, Python raises an error.

Nested indentation¶

Blocks can contain other blocks.

def calculate_fee(x):
    if x < 100:
        fee = x * 0.05
    else:
        fee = x * 0.10
    return fee

print(calculate_fee(80))

6. Common beginner errors¶

If your code does not run, first check:

• missing colons

• inconsistent indentation

• mismatched quotes

• misspelled variable names

7. Summary¶

In this section, you learned:

• identifiers are case sensitive

• comments start with #

• strings require matching quotes

• each line is a statement

• indentation defines structure

Syntax may feel strict, but it enables clarity.
Structure is what makes code readable, maintainable, and reproducible.
Clear structure is essential for reproducible workflows.

Looking ahead¶

In the next section, you will apply your syntax knowledge in a real notebook environment. You will:

• run cells interactively

• observe how execution order matters

• experience how notebooks store variables in memory

Syntax tells Python what your code means. Running notebooks shows you what it does.