Date type Attribute Error, TypeError and all possible errors

Dash Python
1

Hi community,
I am trying to build Manufacturing resource planning system with Python and Dash…
I am using SQLAlchemy to connect to MySQL and write to it. i am having all sorts of fields and type checking’s, but only one that is giving me a headache, starting from input filed formatting, to errors is Date input field…

Here is my input fields, callback and function:
html.H1(“MRP App”),
html.H2(“Master production Scheduling”),
dcc.Input(id=“mps-product-id-input”, type=“number”, placeholder=“Product ID”),
dcc.Input(id=“start-date-input”, type=“Date”, placeholder=“yyyy-mm-dd”),
dcc.Input(id=“end-date-input”, type=“Date”, placeholder=“yyyy-mm-dd”),
dcc.Input(id=“mps-quantity-input”, type=“number”, placeholder=“Quantity”),
dcc.Input(id=“resources-input”, type=“text”, placeholder=“Resources required”),
html.Button(“Create Production Schedule”, id=“create-schedule-button”),
html.Div(id=“schedule-output”),

@app.callback(
Output(“schedule-output”,“children”),
Input(“create-schedule-button”, “n_clicks”),
[
Input(“mps-product-id-input”, “value”),
Input(“start-date-input”, “value”),
Input(“end-date-input”, “value”),
Input(“mps-quantity-input”, “value”),
Input(“resources-input”, “value”)
],
)

def create_production_schedule(n_clicks, product_id, start_date, end_date, quantity, resources):
if n_clicks and product_id and start_date and end_date and quantity and resources:
try:
print(“Start Date:”, start_date)
print(“End Date:”, end_date)
start_date = datetime.strptime(start_date, ‘%Y-%m-%d’).date()
end_date = datetime.strptime(end_date, ‘%Y-%m-%d’).date()
print(“Parsed Start Date:”, start_date)
print(“Parsed End Date:”, end_date)
product_id = int(product_id)
quantity = int(quantity)
except ValueError as e:
print(“ValueError:”, str(e))
return html.Div(“Invalid input. Please provide valid values.”)

    query = "INSERT INTO m_prod_schedule (product_id, start_date, end_date, quantity, resources_required) VALUES (%s, %s, %s, %s, %s)"
    values = (product_id, start_date, end_date, quantity, resources)
    execute_query(query, values)
    return html.Div("Production schedule created successfully!")
else:
    return html.Div("Please fill in all the input fields.")

Firstly, input field for date is not formatting as yyyy-mm-dd even when I enforce pattern
with date type:
dcc.Input(id=“end-date-input”, type=“Date”, placeholder=“yyyy-mm-dd”, pattern=r"\d{4}-\d{2}-\d{2}"),
Pattern shows when type is text, but that raise an error for my function…

Not to write here indefinitely, depending of what i change in my def, i get different errors with datetime, with date, with fromisoformat… or what ever else that i try…
AttributeError: module ‘datetime’ has no attribute ‘strptime’
TypeError: ‘<’ not supported between instances of ‘datetime.date’ and ‘int’

If you can help me with input formatting and how to fix this date type to pass to my database , it will be mostly appreciated!

2

Hi @DataBora , for the Date Input you could check out the nice dash-mantine-components library.

1 Like
3

Based on doc example, it seems that the input type for the date-range-picker component is a list of strings representing dates in the format YYYY-MM-DD

html.Div(
    [
        dmc.DateRangePicker(
            id="date-range-picker",
            label="Date Range",
            description="You can also provide a description",
            minDate=date(2020, 8, 5),
            value=[datetime.now().date(), datetime.now().date() + timedelta(days=5)],
            style={"width": 330},
        ),
        dmc.Space(h=10),
        dmc.Text(id="selected-date-date-range-picker"),
    ]
)


@callback(
    Output("selected-date-date-range-picker", "children"),
    Input("date-range-picker", "value"),
)
def update_output(dates):
    prefix = "You have selected: "
    if dates:
        return prefix + "   -   ".join(dates)
    else:
        raise PreventUpdate

When I make test example:

connection_string = f"mysql+pymysql://{user}:{password}@{host}:{port}/{database}"

# Create the SQLAlchemy engine
engine = create_engine(connection_string)

app = dash.Dash(__name__)

app.layout = html.Div(
    children=[
        html.H1("MRP App"),
        html.H2("Master production Scheduling"),
        dcc.Input(id="mps-product-id-input", type="number", placeholder="Product ID"),
        html.Div(
            [
                dcc.DatePickerRange(
                    id="date-range-picker",
                    start_date_placeholder_text="Start Date",
                    end_date_placeholder_text="End Date",
                    min_date_allowed=date(2020, 8, 5),
                    max_date_allowed=date.today() + timedelta(days=365),
                    initial_visible_month=date.today(),
                    style={"width": 330},
                ),
                html.Div(id="selected-date-date-range-picker"),
            ]
        ),
        dcc.Input(id="mps-quantity-input", type="number", placeholder="Quantity"),
        dcc.Input(id="resources-input", type="text", placeholder="Resources required"),
        html.Button("Create Production Schedule", id="create-schedule-button"),
        html.Div(id="schedule-output"),
    ]
)


@app.callback(
    Output("schedule-output", "children"),
    Input("create-schedule-button", "n_clicks"),
    [
        Input("mps-product-id-input", "value"),
        Input("date-range-picker", "start_date"),
        Input("date-range-picker", "end_date"),
        Input("mps-quantity-input", "value"),
        Input("resources-input", "value"),
    ],
)
def create_production_schedule(n_clicks, product_id, start_date, end_date, quantity, resources):
    if n_clicks and product_id and start_date and end_date and quantity and resources:
        try:
            print("Start Date:", start_date)
            print("End Date:", end_date)
            start_date = datetime.strptime(start_date, '%Y-%m-%d').date()
            end_date = datetime.strptime(end_date, '%Y-%m-%d').date()
            print("Parsed Start Date:", start_date)
            print("Parsed End Date:", end_date)
            product_id = int(product_id)
            quantity = int(quantity)
        except ValueError as e:
            print("ValueError:", str(e))
            return html.Div("Invalid input. Please provide valid values.")

        query = "INSERT INTO m_prod_schedule (product_id, start_date, end_date, quantity, resources_required) VALUES (%s, %s, %s, %s, %s)"
        values = (product_id, start_date, end_date, quantity, resources)
        execute_query(query, values)
        return html.Div("Production schedule created successfully!")
    else:
        return html.Div("Please fill in all the input fields.")


def execute_query(query, values=None):
    with engine.connect() as conn:
        if values is None:
            # Single query without values
            result = conn.execute(text(query))
        else:
            if isinstance(values, list):
                # Multiple queries with values
                result = conn.execute(text(query), values)
            else:
                # Single query with values
                result = conn.execute(text(query), [values])
        return result



if __name__ == "__main__":
    app.run_server(debug=False)

I get similar errors…One of which is: TypeError: ‘<’ not supported between instances of ‘datetime.date’ and ‘int’

4

My guess is that you are trying to compare start date end end date and the order of arguments might be mixed up somewhere.

Where do you do the < comparison ?

5

In what case values can be of type list?

And what does the function text do?

6

I am fully retarded…, I didn’t made comparison…
Here is the function that works with comparison:

def create_production_schedule(n_clicks, product_id, start_date, end_date, quantity, resources):
    if n_clicks and product_id and start_date and end_date and quantity and resources:
        try:
            print("Start Date:", start_date)
            print("End Date:", end_date)
            start_date = datetime.strptime(start_date, '%Y-%m-%d').date()
            end_date = datetime.strptime(end_date, '%Y-%m-%d').date()
            print("Parsed Start Date:", start_date)
            print("Parsed End Date:", end_date)
            product_id = int(product_id)
            quantity = int(quantity)

            # Compare start date and end date
            if start_date > end_date:
                return html.Div("Start date cannot be greater than end date.")

        except ValueError as e:
            print("ValueError:", str(e))
            return html.Div("Invalid input. Please provide valid values.")

        query = "INSERT INTO m_prod_schedule (product_id, start_date, end_date, quantity, resources_required) " \
                "VALUES (:product_id, :start_date, :end_date, :quantity, :resources_required)"
        values = {
            "product_id": product_id,
            "start_date": start_date,
            "end_date": end_date,
            "quantity": quantity,
            "resources_required": resources
        }
        execute_query(query, values)
        return html.Div("Production schedule created successfully!")
    else:
        return html.Div("Please fill in all the input fields.")

For 2 days I am hitting the wall…Thank you my friend!

1 Like
7

Well, at least you found the cause for the error, happy to be of help.

1 Like
8

If values is not a list, it means it executing a single query with a single set of values. In this case, the values parameter is wrapped in a list before passing it to the conn.execute method.
If value is a list, it means you’re executing multiple queries, each with a different set of values. Each element in the values list represents a set of values for a specific query.
In this case, the conn.execute method is called with values list directly

text function is a helper function in SQLAlchemy to create a TextClause object, which represents a SQL statement…

1 Like