如果在每次绘图之前使用plt.figure()命令将每个图形定义为单独的图形，则它们不会相互叠加。例如：

import matplotlib.pyplot as plt
import numpy as np

# Create scatter plot with all the results
x = np.loadtxt("combined_data.txt")[:,0]
y = np.loadtxt("combined_data.txt")[:,1]

plt.figure(1)
plt.plot(x, y, "o")
plt.ylabel("Verbal")
plt.xlabel("Quantitative")

plt.savefig("scores_plot.png")

# Create scatter plot of Quantitative Scores vs. Admissions
y_quant = np.loadtxt("combined_data.txt")[:,0]
x_quant = np.loadtxt("admit_data.txt")[:]

plt.figure(2)
plt.plot(x_quant, y_quant, "o")
plt.ylabel("Quantitative")
plt.xlabel("Admission")

plt.savefig("quant.png")

# Create scatter plot of Verbal Scores vs. Admissions
y_verb = np.loadtxt("combined_data.txt")[:,1]
x_verb = np.loadtxt("admit_data.txt")[:]

plt.figure(3)
plt.plot(x_verb, y_verb, "o")
plt.ylabel("Verbal")
plt.xlabel("Admission")

plt.savefig("verbal.png")

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不要将pyplot接口用于任何超出即时交互式探索的用途。
我会这么做

import matplotlib.pyplot as plt
import numpy as np

# Create scatter plot with all the results
x = np.loadtxt("combined_data.txt")[:,0]
y = np.loadtxt("combined_data.txt")[:,1]

fig1, ax1 = plt.subplots()
ax1.plot(x, y, "o")
ax1.set_ylabel("Verbal")
ax2.set_xlabel("Quantitative")
fig1.savefig("scores_plot.png")

# Create scatter plot of Quantitative Scores vs. Admissions
y_quant = np.loadtxt("combined_data.txt")[:,0]
x_quant = np.loadtxt("admit_data.txt")[:]

fig2, ax2 = plt.subplots()
ax2.plot(x_quant, y_quant, "o")
ax2.set_ylabel("Quantitative")
ax2.set_xlabel("Admission")
fig2.savefig("quant.png")

# yada yada

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