随机生成100000个0到100的成绩，然后分段统计成绩的数量（分为3段：0～59、60～84、85～100）。
参考程序：
import csv,random
import pandas as pd
import matplotlib.pyplot as plt

csvfile = r"d:\python\myscore.csv"
with open(csvfile, 'w') as fp:
    wr = csv.writer(fp)
    wr.writerow(["学号", "成绩"])
    for i in range(100000):
        wr.writerow([str(i+1), random.randrange(101)])
df = pd.read_csv(r"d:\python\myscore.csv", encoding="cp936")
df = df.dropna(axis=0)
plt.figure()
x = df["成绩"]
lx = [0,60,85,101]
ly = ["0-59","60-84","85-100"]
total=[0,0,0]
for i in range(3):
    total[i] = x.between(lx[i], lx[i+1]-1).sum()
plt.plot(ly, total)
print(total)
plt.show()