常见**函数公式及其代码编写(python语言)

**函数：

def sigmoid(x):
    """sigmoid函数"""
    return 1 / (1 + np.exp(-x))

def der_sigmoid(x):
    """sigmoid函数的导数"""
    return sigmoid() * (1 - sigmoid(x))

def tanh(x):
    """tanh函数"""
    return ((np.exp(x) - np.exp(-x)) / (np.exp(x) + np.exp(-x)))

def der_tanh(x):
    """tanh函数的导数"""
    return 1 - tanh(x) * tanh(x)

def relu(x):
    """relu函数"""
    temp = np.zeros_like(x)
    if_bigger_zero = (x > temp)
    return x * if_bigger_zero

def der_relu(x):
    """relu函数的导数"""
    temp = np.zeros_like(x)
    if_bigger_equal_zero = (x >= temp)
    return if_bigger_equal_zero * np.ones_like(x)