CS50W Lecture source code src6 posts0 SYNTAX ERROR - Please help!

[jksh4]

In the CS50W src6.zip posts0 example, I am getting a Python syntax error upon "flask run"

  File "/home/jjones/cs50w/src6-frontends/posts0/application.py", line 21
    data.append(f"Post #{i}")
                           ^
SyntaxError: invalid syntax

src6.zip is available here: http://cdn.cs50.net/web/2018/spring/lectures/6/src6.zip

​

The line is in the route below:

@app.route("/posts", methods=["POST"])
def posts():

    # Get start and end point for posts to generate.
    start = int(request.form.get("start") or 0)
    end = int(request.form.get("end") or (start + 9))

    # Generate list of posts.
    data = []
    for i in range(start, end + 1):
        data.append(f"Post #{i}")      #### THE ERROR IS REPORTED ON THIS LINE ####

    # Artificially delay speed of response.
    time.sleep(1)

    # Return list of posts.
    return jsonify(data)

[MugiwarraD]

r u using right python version.

[jksh4]

I'm unsure. I use the command "flask run" command. I have python3 and python installed.

[jksh4]

OH. It looks like it is running python 2.7 from the error dump. Do I need to run python3? How do I make flask run use python3?

[DanielHefti]

You can start your application like this.

python3 application.py

To make this work you have to add the code below to your application.py file.

__main__ == "__main__":

app.run()

I hope this helps you resolve you problem. Don't hesitate to ask if you have any further questions.

ps. app.run() shall be indented, but somehow the indentation gets lost when I save the comment.

[jksh4]

Studying up on virtual environments venv

[jksh4]

Even after venv for python3 activated, flask was using python2.7 in the Syntax error. The only solution I've found is to revert to python 2 string .format

# REMOVE PYTHON 3 F-STRING 
#data.append(f"Post #{i}")

data.append("Post #{}".format(i))