python 3.x - Calculation raises error "Can't multiply sequence by non-int of type 'float'" -

so, want write program python 3 can users calculate circumference of circle , sphere. far have.

pi = 3.14159 value = input("enter value of radius:") circ = 2*pi*value print(circ)

but, keeps saying "can't multiply sequence non-int of type 'float'". how fix this? and, how make input numbers only? thank you.

try

value = float(input("enter value of radius: "))

note throw error if input isn't number.

also, while cant control input, keep asking number if type else this:

while true: try: value = float(input("enter value of radius: ")) except valueerror: print("please enter number")

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