> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sourcery.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Last if statement guard

#### Sourcery refactoring id: `last-if-guard`

#### Description:

Convert the final conditional into a guard clause

#### Before:

```python
def f(a=None):
    if a is None:
        return 42
    else:
        # some long calculations
        var = (i % 2 for i in range(a))
        return sum(var)
```

#### After:

```python
def f(a=None):
    if a is None:
        return 42

    # some long calculations
    var = (i % 2 for i in range(a))
    return sum(var)
```

#### Explanation:

A common code pattern is to have some clauses at the start of a function, to
check whether certain conditions have been fulfilled and return early or raise
an exception if not.

While this is perfectly valid code, it can run into problems with excessive
nesting, particularly if the rest of the function is fairly long.

Here we can take advantage of the fact that we don't need the `else` if the main
body of the `if` breaks the control flow by ending with `return` or `raise`.
Rewriting the function as shown here is logically equivalent.

Using a guard condition, or multiple guard conditions, in this way now doesn't
cause the rest of the function to be indented. In general the less we have to
deal with indents the easier the code is to understand.