4.3 Statements

1.1 What Is a Statement?

A statement is an instruction that tells Python to do something.

name = "Alex"
print(name)

The first statement stores a name. The second statement displays it.

Python normally runs statements from top to bottom.

1.2 Simple Statements

A simple statement usually fits on one line and performs one action.

server_count = 3              # assignment
print(server_count)            # function call
import platform                # import

Other common simple statements include return, break, and continue inside functions or loops.

1.3 Compound Statements

A compound statement controls a block of code. Its first line ends with a colon, and the lines below it are indented.

server_status = "running"

if server_status == "running":
    print("The server is healthy")

The if line is the header. The indented print() line is the body.

Common compound statements include:

• if for decisions
• for and while for loops
• def for functions
• class for classes
• try for error handling

1.4 Statements with Conditions

An if statement runs its block only when the condition is true:

disk_usage = 70

if disk_usage > 80:
    print("Disk usage is high")
else:
    print("Disk usage is normal")

The else block runs when the if condition is false.

1.5 Statements with Loops

A for statement repeats a block for each item:

servers = ["web-01", "web-02", "web-03"]

for server in servers:
    print(server)

The output is:

web-01
web-02
web-03

1.6 Multiple Statements on One Line

Python allows multiple simple statements on one line with semicolons:

first_name = "Alex"; print(first_name)

However, this style is harder to read. Write one statement per line instead:

first_name = "Alex"
print(first_name)

One statement per line is the usual Python style and makes errors easier to find.

1.7 Long Statements on Multiple Lines

Long statements can be split across lines inside brackets:

server_names = [
    "web-01",
    "web-02",
    "web-03",
]

Python understands that the list continues until the closing bracket.

You can also use parentheses for a long calculation:

total_cost = (
    monthly_compute_cost
    + monthly_storage_cost
    + monthly_network_cost
)

This is easier to read than one very long line.

Avoid using a backslash for line continuation when brackets can be used:

total = (
    first_value
    + second_value
)

1.8 The pass Statement

The pass statement does nothing. It is useful when you want to create a block and add the real code later:

def check_server():
    pass

Without pass, Python would report an error because the function has no body.

1.9 A Complete Example

This example combines assignments, a condition, a function, and a loop:

servers = ["web-01", "web-02"]
healthy_servers = 0


def show_server(server):
    print(f"Checking {server}")


for server in servers:
    show_server(server)
    healthy_servers += 1


print(f"Healthy servers: {healthy_servers}")

1.10 Practice Exercise

Create a program that checks a list of server statuses:

server_statuses = ["running", "stopped", "running"]

for status in server_statuses:
    if status == "running":
        print("Server is healthy")
    else:
        print("Server needs attention")

Change the list and observe how the output changes.

Interview Questions

• What is a statement in Python?
• What is the difference between a simple and compound statement?
• Why does a compound statement need a colon?
• Why is indentation important after a compound statement?
• Can you place multiple statements on one line?
• How can you split a long statement across multiple lines?

Quick Interview Answer

A statement is an instruction for Python to execute. A simple statement usually performs one action on one line, such as an assignment or function call. A compound statement, such as if, for, or def, ends with a colon and contains an indented block. Python allows semicolons, but one statement per line is easier to read.

Key Takeaways

• A statement is an instruction for Python.
• Simple statements usually fit on one line.
• Compound statements contain an indented block.
• Compound statement headers end with a colon.
• Prefer one statement per line.
• Use brackets or parentheses to split long statements. 1 2

## Line Continuation

### What Is It?

Splitting one logical statement across multiple physical lines, either explicitly with a trailing backslash or implicitly inside brackets.

### Why Is It Used?

It keeps long expressions readable instead of one very long line.

### How Is It Used?

See [4.15 Multiple Statements & Line Continuation](../15-multiple-statements-and-line-continuation/) for the full comparison of both styles.

```python
total = 1 + \
        2 + \
        3
>>> total
6

Quick Interview Answer

“A simple statement fits on one line and does one thing — an assignment, a function call, an import. A compound statement has a colon-terminated header and an indented block beneath it — if, for, def, class. You can technically cram multiple simple statements onto one line with semicolons, but PEP 8 discourages it.”

Common Mistakes

• Forgetting the colon at the end of a compound statement’s header line — the single most common beginner SyntaxError.
• Overusing semicolons to combine simple statements, which hurts readability without any real performance benefit.