Python syntax - Programming with Spatial Data

How Python code is structured

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.

Interactive Explorer: Python Syntax Rules.
Click the syntax rules to see how Python reads identifiers, comments, strings, statements, and indentation. Use the broken-code examples to reveal where Python gets confused and how a corrected structure makes the code readable again. For improved visibility of the explorer, follow this link.

1. Identifiers and case¶

An identifier is a name used for variables, functions, and classes.

Example:

x = 5
X = "Harry"

print(x)
print(X)

Python is case sensitive.

x and X are two different identifiers.

Concept check

What will this print?

value = 10
Value = 20
print(value)

A) 10
B) 20
C) Value Error

Think first, then try it.

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 chapter, 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 chapter, 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.