CODEWITHSUNDEEP
pythonflask
simonsays
simonsays

Reputation: 61

Flask - using outputs from a function inside another Function

If I define two functions:

def atesting():
    a = 2
    return a

def btesting():
    b = a+ 3
    return b

But in Flask I get an "Internal Server Error" when running the following if "a" hasn't been defined already. Although if I define "a" outside the app ie say a =2, then it works and I get 5.

app = Flask(__name__)

@app.route('/')
def index():
    results = {}

    a = atesting()

    results = btesting()

    return render_template('index.html', results=results)
if __name__ == '__main__':
    app.run()

Index.html:

<html>

      <h1>{{ results }}</h1>

</html>

But just normally in Python I get 5 when i run this:

a = atesting()
btesting()

Why won't Flask use a = atesting() as an input when computing btesting()?

Upvotes: 0

Views: 2255

Answers (2)

576i
576i

Reputation: 8362

The flask error is correct.

For this usecase there is no global a. (It is set inside the index function, so other functions can't see it)

This is different, if you define a globally in a normal program.

If you want to let function btesting seen the a variable, pass it as a parameter.

app = Flask(__name__)

@app.route('/')
def index():
    results = {}

    a = atesting()

    results = btesting(a)

    return render_template('index.html', results=results)

if __name__ == '__main__':
    app.run()

and 

def btesting(a):
    b = a + 3
    return b

Upvotes: 1

mikeb
mikeb

Reputation: 11267

The way you have it written, btesting cannot see a. You need to understand scope. Try this for your functions - note that we are telling btesting the value of a by passing it as an argument:

def atesting():
    a = 2
    return a

def btesting(a):
    b = a+ 3
    return b

Then, call it like this (pass the value to the function)

app = Flask(__name__)

@app.route('/')
def index():
    results = {}

    a = atesting()

    results = btesting(a)

    return render_template('index.html', results=results)
if __name__ == '__main__':
    app.run()

Upvotes: 1

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