Tkinter将entry.get()转换为整数问题

我正在用Tkinter编写一个程序来计算风值。它采用Rwy航向、风向和风速来计算风，无论是逆风、顺风还是侧风，以及计算出的相关风速。

我得到这个错误：

Traceback (most recent call last):
File "C:UsersaltugDesktopPROJECTSÇALIŞMA.py", line 40, in <module>
rwy_var= int(rwy)
ValueError: invalid literal for int() with base 10: ''

我都尝试了IntVar((和int(str(方法将字符串转换为整数，但它没有解决问题。下面你可以找到我的代码：

ent1 = Entry(root)
ent1.grid(row = 0, column = 1)
ent2 = Entry(root)
ent2.grid(row = 1, column = 1)
ent3 = Entry(root)
ent3.grid(row = 2, column = 1)


rwy = ent1.get()
wind_direction = ent2.get()
wind_speed = ent3.get()
rwy_var= IntVar()
wind_direction_var= IntVar()
wind_speed_var = IntVar()

rwy_var= int(rwy)
wind_direction_var= int(wind_direction)
wind_speed_var = int(wind_speed)
x = rwy_var - wind_direction_var
radx = math.radians(x)
sinx = math.sin(radx)
cosx = math.cos(radx)


def htwind():
txt.delete(0.0, "end")
b = rwy_var + 90
a = rwy_var - 90
if b > 360:
b -= 360
elif a <0:
a+= 360
if x == abs(90):
result = 0
txt.insert(0.0, result +'n')
elif a <= wind_direction_var or  wind_direction_var<= b :
sh = wind_speed_var * cosx
result = "Headwind"+ " " + round(abs(sh))+ " " + "kt"
txt.insert(0.0, result +'n')
elif a >= wind_direction_var or  wind_direction_var >= b :
st = wind_speed_var * cosx
result = "Tailwind"+ " " + round(abs(st))+ " " + "kt"
txt.insert(0.0, result +'n')
return ""

def xwind():
txt.delete(0.0, "end")
c=rwy_var-180
d= rwy_var + 180
if d > 360: 
d -= 360
elif c<0:
c+= 360
if x == 0 or x == abs(180) or y == 0 or y == abs(180):
print("0")
elif c< wind_direction_var:
sxwl = wind_speed_var * sinx
rslt = "L"+""+round(abs(sxwl))+""+"kt"
txt.insert(0.0, rslt +'n')
elif wind_direction_var<d:
sxwr = wind_speed_var * sinx
rslt = "R"+""+round(abs(sxwr))+""+"kt"
txt.insert(0.0, rslt +'n')
return ""



txt = Text(root, width=6, height=2, wrap =WORD)
txt.grid(row =1, column = 1)
button_1 =Button(root, text = "search", command=lambda:[htwind(),xwind()])
button_1.grid(row =0, column = 5)

我犯了什么错？

提前谢谢。