Python matplotlib graph problem

import matplotlib
import matplotlib.pyplot as plt
import pylab as PL

matplotlib.rcParams['axes.unicode_minus'] = False
fig = plt.figure()
ax = fig.add_subplot(111)
PL.loglog(a, b,'o')
ax.set_title(开发者_Go百科'Graph Example')
plt.show()

1) This displays the graph with points on the plot. Is there a way to join these points with a smooth curve.

2) I want to draw more than one plot in the same graph(i.e. for a different set of values of lists a and b) . How do I do that? I want to represent points of each graph with a different symbol(cross,square,circle) or color.

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1. See @Ber's comment
2. Simply call PL.loglog multiple times.