How to make the Qt designer lineEdit receive an integer or float with Python

Question

I would like to know how to make a lineEdit of Qt designer receive a value of type integer or float and armezene that value received in a variable, because, I need to do mathematical operations with it.

By default, lineEdit takes a variable of type str.

I have the following code: >>>>>>>>>>>>>>>>>>>>>>>>>>

def chamar_segunda_tela():
    tela_total.show()
    cursor.execute('SELECT SUM(preco) FROM tb_registrados;')
    for t in cursor.fetchall():
        total = t

        tela_total.label_5.setText(f'{total[0]:>7.2f}')
        tela_total.label_6.setText(f'{total[0]:>7.2f}')

        dinheiro_recebido =  tela_total.lineEdit_3.text()

I’ve tried everything convert in every way, for example: int(screen-total.linEdit_3.text()). I’ve read the documentation, but I can’t find any specific method for integer or floating number. I tried using Qdoublevalidator unsuccessfully, I did the following:

def chamar_segunda_tela():
    tela_total.show()
    cursor.execute('SELECT SUM(preco) FROM tb_registrados;')
    for t in cursor.fetchall():
        total = t

        tela_total.label_5.setText(f'{total[0]:>7.2f}')
        tela_total.label_6.setText(f'{total[0]:>7.2f}')

        validacao_regra = QDoubleValidator(0.0, 5.0, 2)

        dinheiro_recebido =  tela_total.lineEdit_3.setValidator(validacao_regra)
        dinheiro_lol = tela_total.lineEdit_3.setText(dinheiro_recebido)

        print(dinheiro_recebido, type(dinheiro_recebido))
        print(dinheiro_lol, type(dinheiro_lol))

But then he returns me None<class: None Type> . I read about Inputmask, but I didn’t understand how to implement it. I find the documentation very confusing.

Can someone help me ??

Answer 1

Guys, I solved the problem, before I used this code:

def chamar_segunda_tela():
    tela_total.show()
    cursor.execute('SELECT SUM(preco) FROM tb_registrados;')
    for t in cursor.fetchall():
        total = t

        tela_total.label_5.setText(f'{total[0]:>7.2f}')
        tela_total.label_6.setText(f'{total[0]:>7.2f}')

        dinheiro_recebido = tela_total.lineEdit.text() # Esse código era o problema, dava erro e não conseguia converter de str para float

And I needed the lineEdit to be a float type actually, so I could bill and print the change on the screen. And when I tried to convert, it returned the error "(<class 'Valueerror'>, Valueerror("could not Convert string to float: ''"), <traceback Object at 0x00000227F6FF0500>)"

I tried to convert it this way:

dinheiro_recebido = float(tela_total.lineEdit.text())

I saw many users converting so without problems, but only my code gave problems, after breaking the head, a boy helped me and the solution found by her was to create another function and this time it worked, he was able to perform the conversion from str to float without major problems.

def chamar_segunda_tela(): # Essa tela exibe o total da compra e o total a pagar (que basicamente são a mesma coisa)
    cursor = mydb.cursor()
    tela_total.show()

    cursor.execute(f'SELECT SUM(preco) FROM tb_registrados;')
    for t in cursor.fetchall():
        total = t
        tela_total.label_5.setText(f'{total[0]:>7.2f}')
        tela_total.label_6.setText(f'{total[0]:>7.2f}')
    cursor.close()

def tela_pagamento(): # Essa tela é a mesma que a anterior, apenas foi necessário criar a função de receber o dinheiro e imprimir o troco em uma função separada 
    cursor = mydb.cursor()
    dinheiro_recebido = float(tela_total.lineEdit.text()) # Aqui a conversão não deu mais erro.
    tela_total.lineEdit.clear()

    cursor.execute(f'SELECT SUM(preco) FROM tb_registrados;')
    for t in cursor.fetchall():
        total = t
        print(total, type(total), type(total[0]))
        troco = dinheiro_recebido - total[0]

        tela_total.label_7.setText(f'{troco:>7.2f}')

I attached an image to view the interface working. Thank you all for your attention !