python数学计算中内存释放问题，劳烦各位大牛赐教

本人刚开始学python，主要是想做数据计算、分析和处理。在计算过程中，遇到了Memory error
网上也查了不少资料，主要是内存耗尽，每次计算时计算到固定次数就提示Memory error.下面
是我的代码，麻烦各位大牛帮忙看看：
import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import quad
import time
from scipy import special
import xlwt
from itertools import product

def R(t):
confidence = 0
for num in range(0, 5):
confidence = confidence + np.power(t / 400, num) * np.exp(-t / 400) / special.factorial(num)
return confidence

def g(a, t):
return 1 - a * R(t)

def q(β, t):
return 1 - β * R(4000 - t)

def A(a, β, t):
if t < 500:
return quad(lambda t: R(t), 0, t)[0] / 3500
elif (t > 499 and t < 2907):
return quad(lambda t: a * R(t) ** 2, 0, t)[0] / 3500
elif t == 2907:
return quad(lambda t: a * R(t) ** 2, 0, 2907)[0] / 3500
elif (t > 2907 and t < 3460):
return (quad(lambda t: a * R(t) ** 2, 0, 2907)[0] +
quad(lambda t: β * R(4000 - t) * R(t), 2907, t)[0]) / 3500
elif t == 3460:
return (quad(lambda t: a * R(t) ** 2, 0, 2907)[0] +
quad(lambda t: β * R(4000 - t) * R(t), 2907, 3460)[0]) / 3500
else:
print("超出寿命周期边界")

def MAX(l):
first = [0]
t = list(range(1, 3461))
for i in range(0, len(l)):
if l[i] > first[0]:
first[0] = l[i]
else:
continue
for i in range(0, len(l)):
if l[i] == first[0]:
print("可靠度最大值是%0.3f" % (l[i]))
print("可靠度最大值是对应的时间等于：%0.2f" % (t[i]))
tmax = t[i]
return first[0], tmax

start = time.clock()

初始化抽样参数

N1 = int(input("你想对a和β抽样多少次"))
n1 = 1

xishus = []

At = []

Atjifen = 0

book = xlwt.Workbook(encoding='utf-8', style_compression=0)
sheet1 = book.add_sheet("可用度", cell_overwrite_ok=False)
sheet2 = book.add_sheet("可用度积分", cell_overwrite_ok=False)
sheet1.write(0, 0, '抽样次数')
sheet1.write(0, 1, "可用度最大值")
sheet1.write(0, 2, "对应时间")
sheet1.write(0, 3, "过评估系数a")
sheet1.write(0, 4, "过评估系数β")
sheet2.write(0, 0, '抽样次数')
sheet2.write(0, 1, "可用度积分")
sheet2.write(0, 2, "过评估系数a")
sheet2.write(0, 3, "欠评估系数β")

amiddle = np.arange(1, 100, 25)

βmiddle = np.arange(1, 100, 25)
aβ = list(product(amiddle, βmiddle))
for i in aβ:
a = i[0] / 100
β = i[1] / 100
ts = list(range(1, 3461))

for t in ts:
    y = A(a, β, t)
    At.append(y)
AT = MAX(At)

sheet1.write(n1, 0, n1)
sheet1.write(n1, 1, AT[0])
sheet1.write(n1, 2, AT[1])
sheet1.write(n1, 3, a)
sheet1.write(n1, 4, β)


for middleA in At:
    Atjifen = Atjifen + middleA

sheet2.write(n1, 0, n1)
sheet2.write(n1, 1, Atjifen)
sheet2.write(n1, 2, a)
sheet2.write(n1, 3, β)
At = []
print("计算次数：" + str(n1))
n1 = n1 + 1
Atjifen = 0

print(time.clock() - start)
book.save("E:/1.xls")

以上就是我的代码，期间尝试用过del删除变量，用过gc.collect()，发现都没起作用。
也想使用numpy.array，但是条件函数A出错，实在无计可施了。