TypeError: unorderable types: str() <= int() error
<p>Could you guys help me out with finding the wrong part of the code? I tried some things and searched on this site, but I couldn't find the solution.. If you guys know something, please let it know :D</p>

<pre><code>print("Uw formule is ax**2+bx+c")
a= float(input("Geef getal a:" ))
b= float(input("Geef getal b:" ))         
c= float(input("Geef getal c:" ))
D=b**2-4*a*c

while (D&lt;=0) or (a==0):
    print("Voer nieuwe getallen in, de uitkomst is niet te berekenen")
    a= float(input("Geef getal a:" ))
    b= float(input("Geef getal b:" ))
    c= float(input("Geef getal c:" ))
    D=b*b-4*a*c
    D= format(D,'.1f')

if (D&gt;0):
    print("\nDe discriminant is:", D )
    x1= (-b-(D)**0.5)/(2*a)
    x1= format(x1,'.1f')
    x2= (-b+(D)**0.5)/(2*a)
    x2= format(x2,'.1f')

print("De uitkomst van x1=", x1)
print("De uitkomst van x2=", x2)  
</code></pre>

<p>Then the error:</p>

<pre><code>Traceback (most recent call last):
  File "*****", line 15, in &lt;module&gt;
    while (D&lt;=0) or (a==0):
TypeError: unorderable types: str() &lt;= int()
</code></pre>

<p>Thanks! I solved it with:</p>

<pre><code>print("Uw formule is ax**2+bx+c")
a= float(input("Geef getal a:" ))
b= float(input("Geef getal b:" ))         
c= float(input("Geef getal c:" ))
D=b**2-4*a*c

while (D&lt;=0) or (a==0):
    print("Voer nieuwe getallen in, de uitkomst is niet te berekenen")
    a= float(input("Geef getal a:" ))
    b= float(input("Geef getal b:" ))
    c= float(input("Geef getal c:" ))
    D=b*b-4*a*c
    D1= format(D,'.1f')  #this code

if (D&gt;0):
    print("\nDe discriminant is:", D1 )
    x1= (-b-(D)**0.5)/(2*a)
    x1= format(x1,'.1f')
    x2= (-b+(D)**0.5)/(2*a)
    x2= format(x2,'.1f')

print("De uitkomst van x1=", x1)
print("De uitkomst van x2=", x2)  
</code></pre>

python