python - sigmoid

import numpy as np
import matplotlib.pyplot as plt
import tensorflow as tf

def sigmo(x):
    a = list() # list
    for i in x:
        a.append(1/(1 + np.exp(-i)))
    return a

def main():
    x = np.linspace(start=-8.0, stop=8.0, num=10000)
    sig = sigmo(x)
    plt.plot(x, sig)
    plt.show()

if __name__ == "__main__":
    main()