Python3.6下Flask视图函数遇namedtuple标识符错误，求助排查

Hey there! Let's break down why you're seeing this error when working with namedtuple in your Flask view function. This error pops up when either the type name you give your namedtuple or one of its field names isn't a valid Python identifier. Here are the most common culprits and how to fix them:

Common Causes & Solutions #

1. Using a Python keyword as a name #

Python has reserved keywords (like def, class, return, import) that can't be used as identifiers. If you try to name your namedtuple or one of its fields with a keyword, you'll hit this error immediately.

Bad Example:

from collections import namedtuple
# Invalid: 'class' is a reserved keyword
User = namedtuple('User', ['class', 'age'])
# Also invalid: 'def' can't be the type name
BadTuple = namedtuple('def', ['name', 'id'])

Fix:
Pick a name that's not a keyword. For example, rename class to user_class or role:

User = namedtuple('User', ['user_class', 'age'])

2. Using invalid characters in names #

Identifiers can only contain letters, numbers, and underscores. They also can't start with a number, or include spaces, hyphens, or other special characters.

Bad Example:

# Invalid: Field name has a space
User = namedtuple('User', ['full name', 'email'])
# Invalid: Type name starts with a number
InvalidTuple = namedtuple('123User', ['name', 'age'])
# Invalid: Field name uses a hyphen
User = namedtuple('User', ['user-id', 'age'])

Fix:
Replace spaces/hyphens with underscores, and avoid leading numbers:

User = namedtuple('User', ['full_name', 'email'])
ValidTuple = namedtuple('User123', ['name', 'age'])
User = namedtuple('User', ['user_id', 'age'])

3. Conflicting with namedtuple built-in methods #

namedtuple comes with built-in methods like _asdict(), _replace(), and _fields. If you use one of these names as a field, Python will throw an error because it's trying to overwrite a reserved method.

Bad Example:

# Invalid: '_asdict' is a reserved method name
User = namedtuple('User', ['_asdict', 'name'])

Fix:
Rename the field to something unique, like as_dict or user_data:

User = namedtuple('User', ['user_data', 'name'])

4. Mistyping field names when using a string #

If you pass field names as a space-separated string (instead of a list), extra commas or typos can create invalid field names.

Bad Example:

# Invalid: Trailing comma creates an empty field name
User = namedtuple('User', 'name, age, ')

Fix:
Stick to a list of field names for clarity, or ensure the string is clean:

# Preferred approach: List of fields
User = namedtuple('User', ['name', 'age'])
# If using a string: No extra commas/spaces
User = namedtuple('User', 'name age')

Quick Checks to Validate Names #

If you're unsure if a name is valid, use these quick tests in your Python shell:

# Check if a string is a valid identifier
print('full_name'.isidentifier())  # Returns True
print('123user'.isidentifier())  # Returns False

# Check if a name is a Python keyword
import keyword
print(keyword.iskeyword('class'))  # Returns True

If you're still stuck, sharing a snippet of the namedtuple code from your Flask view would help narrow it down further!

内容的提问来源于stack exchange，提问作者user1592380