How can I exert greater control over a sequence of functions?

I am struggling to execute my functions in the intended sequence. By that, I mean each of the functions below depend on the creation of files by the preceding function in order to execute. I have reviewed the docs and viewed the videos about callbacks, but I don’t see much information about how to use them to control timing issues. I understand that’s possible, but what does it look like? As shown below, I tried to use the the "if file “exists” strategy, but it did not work. I still receive a “file not found” error message. I even tried to use the time.sleep() method to delay their execution, but that’s not a good solution. Not at all :slight_smile:

Any constructive feedback is welcome.

app = dash.Dash(__name__)

app.layout = html.Div([




        style={'width': '100%', 'height': 200},

        placeholder='Please note: Information inside brackets or parantheses will be deleted.'


    html.Button('Submit', id='textarea-state-example-button', n_clicks=0),


             style={'whiteSpace': 'pre-line'})



    Output('textarea-state-example-output', 'children'),

    Input('textarea-state-example-button', 'n_clicks'),

    State('textarea-state-example', 'value')


def submit_recipe(n_clicks, value):

    if n_clicks > 0:

        with open("temp/recipe_contents.txt", "w", encoding='utf-8') as recipe_contents:

            recipe = value.split('\n')

            for line in recipe:




            return "Recipe contents written to file."

def convert_unicode_fractions(n_clicks, value):

    if n_clicks > 0:

        if os.path.exists('temp/recipe_contents.txt'):

            print("recipe_contents.txt exists")

            vulgar_fractions = convert_unicode_fractions()

            print("Output: Convert Unicode Fractions")


            print(" ")

            return "Recipe is cleared of unicode fractions"

def convert_regular_fractions(n_clicks, value):

    if n_clicks > 0:

        if os.path.exists('temp/vulgar_free_recipe.txt'):

            print("vulgar_free_recipe.txt exists")

            common_fractions = convert_regular_fractions()

            print("Output: Convert Unicode Fractions")


            print(" ")

            return "Recipe is cleared of regular fractions"

def clean_recipe_textacy(n_clicks, value):

    if n_clicks > 0:

        if os.path.exists('temp/fraction_free_recipe.txt'):

            print("fraction_free_recipe.txt exists")

            clean_text = clean_recipe_text()

            print("Output: Convert Unicode Fractions")


            print(" ")

            return "Recipe text is cleaned by textacy."

if __name__ == '__main__':

    app.run_server(debug=True, dev_tools_silence_routes_logging=False)

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