import numpy as np
a = 3.9 #m
L = 7.8 #m
x = np.arange(0,L+0.1,0.1)
def fun_v():
for value in x:
if 0 < x < a :
V= P*(1-(a/L))
if a < x < L :
V= -P*(a/L)
return (V)
V = fun_v()
print('V =',V)
#ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
The issues are the following:
You are comparing an array instead of a value in a condition, which is ambiguous.
Try 0 < value < a instead 0 < x < a
To give an example of what you are doing:
x like [0, 0.1, 0.2, 0.3 ... ]0 < [0, 0.1, 0.2, 0.3 ... ] < 3.9 at line 0 < x < aAlso, the variable P is not defined. You will need to provide a value of P like the ones you provide for a and L.
To get an array of V values, you will need to push the calculated V values in an empty array or you can use the map function.
A working example:
import numpy as np
a = 3.9
L = 7.8
P = 10 # P is defined
x = np.arange(0,L+0.1,0.1)
def fun_v():
arr = [] # empty array is initialized
for value in x:
if 0 < value < a : # value is compared instead of x
V = P*(1-(a/L))
arr.append(V) # V is pushed after calculation
if a < value < L :
V = -P*(a/L)
arr.append(V)
return arr # return the array of v values
V = fun_v()
print(V)
I think the comparison is wrong and you didn't declare what is p. I am actually not sure what you trying to do at the end as it wont return anything. but from your code, I believe it suppose to be like this:
import numpy as np
a = 3.9 #m
L = 7.8 #m
x = np.arange(0,L+0.1,0.1)
def fun_v(x_):
for value in x_:
P = 1 # declare your P value
if 0 < value < a:
V = P*(1-(a/L))
elif a < value < L:
V = -P*(a/L)
return V
V = fun_v(x)
print(V)
But in this code, the V value will not be an array or list. it will just return a value. if you would like to calculate all the x value and separate it in different list or array, you might need an append.
You can do it with a fancy indexing technique of NumPy, which will be both quicker and easier to comprehend:
import numpy as np
a = 3.9 #m
L = 7.8 #m
P=1
x = np.arange(0,L+0.1,0.1)
x[(0<x)&(x>a)]=P*(1-(a/L))
x[(a<x)&(x>L)]=-P*(a/L)
x
xin the for loop. Maybe you meant0 < value < aanda < value < L0<x<aexpression or in anif. Those only work for single values, not multiple.