单位怎么发年终奖才能合理避税，用Python程序实现

# -*- coding: utf-8 -*-
def get_tax(x, is_year =False):
if(is_year):
p =x/12.
else:
p =x
if(p<=1500):
return x *.03
elif(p<=4500):
return x*.10 -105
elif(p<=9000):
return x*.20-555
elif(p<35000):
return x*.25-1005

#年终奖 税前、税后计算方法
#pre_taxs =[]
#after_taxs =[]
#for a in range(10*10000):
#pre_tax = a
#pre_taxs.append(pre_tax)
#after_taxs.append( pre_tax -get_tax(pre_tax,is_year=True))

#import matplotlib.pyplot as plt
#plt.plot(pre_taxs, after_taxs)
#plt.show()
####
#应税额度 = 个人工资总额 - 公积金10%-医保80-每月免税部分3500
pre_year_money = int( 128400*.9 -(3500+80)*12) #128400为工资总额

year_end_bonus_list=[] #年终奖所得
month_tax_part_list=[] #含税级距，月税前所得为month_tax_part + 3500
tax_list =[] #全年的个人所得税数
min_tax = pre_year_money #最少纳税额度
min_year_end_bonus = None # 最少纳税额度下对应的年终奖数
min_month_tax_part =None #   最少纳税额度下对应的月含税级据
for year_end_bonus in range(int(pre_year_money)):
month_tax_part  = (pre_year_money - year_end_bonus)/12.
tax = get_tax(year_end_bonus,is_year=True)+ 12* get_tax(month_tax_part) #年终奖扣税部分+ 月个人所得税部分
year_end_bonus_list.append(year_end_bonus)
tax_list.append(tax)
if(min_tax > tax):
min_tax = tax
min_year_end_bonus = year_end_bonus
min_month_tax_part = month_tax_part

print min_tax, min_year_end_bonus,min_month_tax_part+3500

#import matplotlib.pyplot as plt
#plt.plot(year_end_bonus_list, tax_list)
#import matplotlib
#zhfont1 = matplotlib.font_manager.FontProperties(fname='C:\Windows\Fonts\STKAITI.TTF')
#plt.xlabel(u'年终奖数',fontproperties=zhfont1)
#plt.ylabel(u'年个人所得税',fontproperties=zhfont1)
#plt.title(u'不同发放方法下的个人所得税（工资总额固定）',fontproperties=zhfont1)
#plt.show()

mymin_tax = ((8050-3500)*.20-555)*12 + 18000*.03
assert int(mymin_tax) == min_tax
assert 8050*12+ 18000+ 12840+80*12  ==128400