“从 flask 导入烧瓶”中的语法错误

Question

After installing Flask, When I used

from flask import Flask

to check if flask is properly installed or not, it gave the following error

>>> from flask import Flask
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/dist-packages/flask/__init__.py", line 3, in <module>
    from werkzeug.exceptions import abort
  File "/usr/local/lib/python3.5/dist-packages/werkzeug/__init__.py", line 1, in <module>
    from .serving import run_simple
  File "/usr/local/lib/python3.5/dist-packages/werkzeug/serving.py", line 151
    server: "BaseWSGIServer"
          ^
SyntaxError: invalid syntax

How to solve this issue.

Answer 1

The error indicates that you're running Python 3.5. Variable annotations that the library is attempting to use weren't introduced until 3.6 though .

Upgrade to at least 3.6 to solve this. 3.9 is available too, so unless you need to use an older version for some reason, you might as well just to a full upgrade of your version.

Answer 2

Flask is now at 2.0.0, and has ratcheted forward on requirements.

If you're on a system that is still on Python3.5, you are out of luck for 2.0.0. Your alternative is to install the most recent in the 1.x line.

Specify

Flask==1.4.4

if you're using requirements.txt , or

venv/bin/pip install Flask==1.1.4

to install it manually.

Answer 3

Flask is now at 2.0.0, which has ratcheted forward on requirements.

If you're on a system that is still on Python3.5, your alternative is to install the most recent in the 1.x line, and put

Flask==1.1.4

in your requirements.txt , or

venv/bin/pip install Flask==1.1.4

to install it manually.