breakpoint() and pdb Basics¶

Use breakpoint() to start the debugger and understand pdb for interactive debugging.

breakpoint() Function¶

Add breakpoints to pause execution for inspection.

```python def calculate(x, y): result = x + y breakpoint() # Debugger will start here return result * 2

When executed, this will start pdb debugger¶

You can inspect variables and step through code¶

print("Debugger example") ```

``` Debugger example

/path/to/script.py(3)calculate() -> breakpoint() ```

pdb Basics¶

Understand pdb debugger and basic commands.

```python import pdb

def debug_function(items): total = 0 for i, item in enumerate(items): # Start debugger at specific point if item > 5: pdb.set_trace() total += item return total

Debugger commands:¶

l - list code¶

n - next line¶

s - step into function¶

c - continue¶

p variable - print variable¶

pp dict - pretty print¶

result = debug_function([1, 2, 3, 6, 7]) print(f"Result: {result}") ```

Result: 19

Exercises¶

Exercise 1. Write a function find_first_negative that takes a list of numbers and returns the index of the first negative number. Insert a breakpoint() call just before the return statement so you can inspect the variables when debugging. Remove the breakpoint after testing. For example, find_first_negative([3, 7, -2, 5]) should return 2.

Exercise 2. Write a function debug_dict_merge that takes two dictionaries and merges them. If there are duplicate keys, the function should keep the higher value. Add a conditional pdb.set_trace() that only triggers when a duplicate key is found. For example, debug_dict_merge({"a": 1, "b": 5}, {"b": 3, "c": 4}) should return {"a": 1, "b": 5, "c": 4}.

Exercise 3. Write a function trace_recursive_sum that recursively sums a list of numbers. Use breakpoint() with a condition to only pause when the list has exactly 2 elements remaining. This demonstrates conditional breakpoint placement for debugging recursion.