here's my first code, using numpy.linspace method:
import numpy as np
import matplotlib.pyplot as plt
def graph(formula, string, x1, x2):
x = np.linspace(x1, x2)
y = formula(string, x)
plt.plot(x, y)
def my_formula(string, x):
return eval(string)
graph(my_formula, "2 * (x ** 3) - 9.5 * (x ** 2) + 10.5 * x", 0, 3)
plt.tight_layout()
plt.show()
it works fine, however, instead of importing numpy, if I do this:
import matplotlib.pyplot as plt
class Module:
@staticmethod
def linspace(finish, slices, start=0):
each = float((finish - start) / (slices - 1))
res = list()
for i in range(slices):
res.append(start + i * each)
return res
def graph(formula, string, x1, x2):
x = Module.linspace(x2, 50, start=x1)
y = formula(string, x)
plt.plot(x, y)
def my_formula(string, x):
return eval(string)
graph(my_formula, "2 * (x ** 3) - 9.5 * (x ** 2) + 10.5 * x", 0, 3)
plt.tight_layout()
plt.show()
Here's a error shows up:
Traceback (most recent call last):
File "C:/Users/QINY/PycharmProjects/begin/covid/seven.py", line 24, in <module> graph(my_formula, "2 * (x ** 3) - 9.5 * (x ** 2) + 10.5 * x", 0, 3)
File "C:/Users/QINY/PycharmProjects/begin/covid/seven.py", line 16, in graph y = formula(string, x) File "C:/Users/QINY/PycharmProjects/begin/covid/seven.py", line 21, in my_formula return eval(string)
File "<string>", line 1, in <module> TypeError: unsupported operand type(s) for ** or pow(): 'list' and 'int'
Can anyone explain how it is done in numpy.adarray, to automatically iterate the list?
They use Standard operators as functions .
Their type supports functions like __pow__
, __mul__
, __add__
, etc... with implementations that apply the operations on each element of the ndarray
(very efficiently...)
You can make your own type that inherits from list
and have it implement these member functions, iterating the list yourself, applying it on every element.
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