ast.FunctionDef cannot find functions under if statement

[Zero0one1]

BPO	46980
Nosy	@JelleZijlstra, @lysnikolaou, @pablogsal, @Zero0one1

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-03-11.04:09:18.289>
created_at = <Date 2022-03-11.03:08:56.757>
labels = ['interpreter-core', 'invalid', 'type-feature', '3.7']
title = 'ast.FunctionDef cannot find functions under if statement'
updated_at = <Date 2022-03-11.07:01:38.467>
user = 'https://github.com/Zero0one1'

bugs.python.org fields:

activity = <Date 2022-03-11.07:01:38.467>
actor = 'Ruishi'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-11.04:09:18.289>
closer = 'JelleZijlstra'
components = ['Parser']
creation = <Date 2022-03-11.03:08:56.757>
creator = 'Ruishi'
dependencies = []
files = []
hgrepos = []
issue_num = 46980
keywords = []
message_count = 4.0
messages = ['414886', '414887', '414888', '414891']
nosy_count = 4.0
nosy_names = ['JelleZijlstra', 'lys.nikolaou', 'pablogsal', 'Ruishi']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46980'
versions = ['Python 3.7']

[Zero0one1]

When I use the Python ast package to get the functions of Python files, I find the functions defined in the body of if statement cannot be recognized.

Here is my code:
with open(py_file, 'r') as f:
data = f.read()
module = ast.parse(data)
func_def = [node for node in module.body if isinstance(node, ast.FunctionDef)]

Here is an example of Python file:
if supports_bytes_environ:
def _check_bytes(value):
if not isinstance(value, bytes):
raise TypeError("bytes expected, not %s" % type(value).__name__)
return value

The function _check_bytes is not in func_def. I also tested ast.iter_child_nodes(module) and it also has this issue.

[Zero0one1]

I'm not sure whether I should file this issue here or on Github and I'm not an expert on this so I think I cannot contribute to this but only report to you.

[JelleZijlstra]

This is the right place to file an issue.

Your code is incorrect; it will find only top-level functions. Functions within an if statement will be nested inside an ast.If node. To find all functions in a file, you'll need to recurse into nested nodes. For example, you could use ast.walk, an ast.NodeVisitor, or manually check for nodes like ast.If. Which one is best depends on your needs. For example, the first two will also find methods in classes. The ast module documentation has more information.

[Zero0one1]

I see. It's my misunderstanding. Thank you for your help!