QLineEditへ入力なしならば0にする方法

Question

前提・実現したいこと

下のようなGUIにおいて，AzimuthとDistanceに値を入力してCalculateを押すと緯距と経距の計算ができるプログラムを作りました．
これにおいて，AzimuthとDistanceの入力欄で入力がなかった場合は，0が入力されたとして計算できるようにしたいです．

発生している問題・エラーメッセージ

今のプログラムでは，入力がなければ以下のようなエラーメッセージが出ます．

PS C:\Users\survey\Documents\traum\py_calc_lat_lon> python .\factorial_latlon.py
Traceback (most recent call last):
  File ".\factorial_latlon.py", line 102, in calc
    min = int(self.inputMinute.text())
ValueError: invalid literal for int() with base 10: ''

該当のソースコード

#!/usr/bin/env python
#have to convert to radian

from PyQt5.QtWidgets import (QApplication, QWidget,
                             QGridLayout, QVBoxLayout, QHBoxLayout,
                             QLabel, QLineEdit, QPushButton)
from math import *
from decimal import Decimal, ROUND_HALF_UP


#how2calculate
def conv2deg(deg,min,sec):
    go_deg = deg+min/60+sec/3600
    return go_deg

def deg2rad(deg):
    rad = radians(deg)
    return rad

def calc_lat(distance,rad):
    lat = distance * cos(rad)
    return lat

def calc_lon(distance,rad):
    lon = distance * sin(rad)
    return lon

def factorial(n):
    if n < 0:
        return -1
    elif n == 0:
        return 1
    else:
        return n * factorial(n-1)#calcuation
#GUI
class MainWindow(QWidget):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        #input
        self.inputDegree = QLineEdit()
        self.inputMinute = QLineEdit()
        self.inputSecond = QLineEdit()
        self.inputDistance = QLineEdit()
        #output
        self.outputLat = QLineEdit()
        self.outputLat.setReadOnly(True)
        self.outputLon = QLineEdit()
        self.outputLon.setReadOnly(True)
        #button
        self.calcButton = QPushButton("&Calculate")
        self.calcButton.clicked.connect(self.calc)
        #place_input for Azimuth
        lineLayout_1 = QGridLayout()
        lineLayout_1.addWidget(QLabel("Azimuth"), 0, 0)
        lineLayout_1.addWidget(self.inputDegree, 0, 1)
        lineLayout_1.addWidget(QLabel("°"), 0, 2)
        lineLayout_1.addWidget(self.inputMinute, 0, 3)
        lineLayout_1.addWidget(QLabel("'"), 0, 4)
        lineLayout_1.addWidget(self.inputSecond, 0, 5)
        lineLayout_1.addWidget(QLabel("''"), 0, 6)
        #place_input for Distance
        lineLayout_3 = QGridLayout()
        lineLayout_3.addWidget(QLabel("Distance"),0,0)
        lineLayout_3.addWidget(self.inputDistance, 0, 1)

        lineLayout_2 = QGridLayout()
        lineLayout_2.addWidget(QLabel("緯距(X)"), 0, 0)
        lineLayout_2.addWidget(self.outputLat, 0, 1)
        lineLayout_2.addWidget(QLabel("経距(Y)"), 0, 2)
        lineLayout_2.addWidget(self.outputLon, 0, 3)

        buttonLayout = QVBoxLayout()
        # buttonLayout = QHBoxLayout()
        # buttonLayout.addLayout(lineLayout_1)
        # buttonLayout.addLayout(lineLayout_2)
        buttonLayout.addWidget(self.calcButton)

        # mainLayout = QHBoxLayout()
        mainLayout = QVBoxLayout()
        mainLayout.addLayout(lineLayout_1)
        mainLayout.addLayout(lineLayout_3)
        mainLayout.addLayout(lineLayout_2)
        # mainLayout.addLayout(buttonLayout)

        # buttonLayout = QVBoxLayout()
        AllLayout = QHBoxLayout()
        AllLayout.addLayout(mainLayout)
        AllLayout.addLayout(buttonLayout)
        # buttonLayout.addLayout(lineLayout_2)
        # buttonLayout.addWidget(self.calcButton)

        self.setLayout(AllLayout)
        self.setWindowTitle("緯距・経距計算")

    # def calc(self):
    #     n = int(self.inputLine.text())##input
    #     r = factorial(n)
    #     self.outputLine.setText(str(r))
    
    def calc(self):
        deg = int(self.inputDegree.text())
        min = int(self.inputMinute.text())
        sec = int(self.inputSecond.text())
        distance = float(self.inputDistance.text())
        # n = int(self.inputLine.text())##input
        all_deg = conv2deg(deg,min,sec)
        # r = factorial(n)
        rad = deg2rad(all_deg)
        lat = calc_lat(distance,rad)
        lon = calc_lon(distance,rad)
        round_lat = round(lat,3)
        round_lon = round(lon,3)
        round_lat = Decimal(round_lat).quantize(Decimal('0.001'), rounding=ROUND_HALF_UP)
        round_lon = Decimal(round_lon).quantize(Decimal('0.001'), rounding=ROUND_HALF_UP)
        self.outputLat.setText(str(round_lat))
        self.outputLon.setText(str(round_lon))
        # self.outputLat.setText(Decimal(str(round_lat)).quantize(Decimal('0.001',rounding = ROUND_HALF_UP)))
        # self.outputLon.setText(str(round_lon))

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    main_window = MainWindow()

    main_window.show()
    sys.exit(app.exec_())

補足情報（FW/ツールのバージョンなど）

Windows10 64bit, Python 3.5.5

Answer 1

AzimuthとDistanceの入力欄で入力がなかった場合は，0が入力されたとして計算できるようにしたい

条件を満たすだけなら。

deg = int(self.inputDegree.text() or '0')
min = int(self.inputMinute.text() or '0')
sec = int(self.inputSecond.text() or '0')

Comments

[LenItsuki]

できました．適切なアドバイス，どうもありがとうございます．