Python,如何在不复制循环的情况下将if语句移到for循环之外
我可以用两种方法编写函数Python,如何在不复制循环的情况下将if语句移到for循环之外,python,loops,optimization,Python,Loops,Optimization,我可以用两种方法编写函数 def output_ip_hist(target, final, stats, table_name, bulk_qty, type = "sql"): if(type == "sql"): field_names = ",".join(get_field_names(final, table_name)) count = 0 stats[table_name] = 0 values = []
def output_ip_hist(target, final, stats, table_name, bulk_qty, type = "sql"):
if(type == "sql"):
field_names = ",".join(get_field_names(final, table_name))
count = 0
stats[table_name] = 0
values = []
for comp_name, row in final.items():
for ip_address, sub_row in row.items():
for index, ip_hist in enumerate(sub_row):
hist_item = ip_hist.replace('"', "'")
values.append('("' + comp_name + '", "' + ip_address + '", ' + str(index) + ',"' + hist_item + '")')
count += 1
if(count == bulk_qty):
insert_sql_many(target, count, table_name, field_names, values, stats)
count = 0
values = []
if(count != 0):
insert_sql_many(target, count, table_name, field_names, values, stats)
elif(type == "csv"):
for comp_name, row in final.items():
for ip_address, sub_row in row.items():
for index, ip_hist in enumerate(sub_row):
insert_csv(target, { "computer_name": comp_name, "id": str(index), "ip_address": ip_address, "hist_item": ip_hist.replace('"', "'") }, stats, table_name)
这是第一条路。这种方法的缺点是循环被写入两次,从而产生一些重复
第二种方法是将最外层的if语句移动到循环中,这样循环只完成一次,但这样做的缺点是if语句会在每个循环上执行,从而减慢了循环速度,循环可能会通过400万条记录
我想知道是否有可能做到两全其美,减少重复并尽可能快地保持循环
谢谢 您可以定义两个函数:
process\u sql
和process\u csv
。根据数据类型
,您可以将处理数据
设置为第一个功能或第二个功能
在循环内部,您可以使用处理数据
:
def process_sql(a,b):
print "SQL"
return a-b
def process_csv(a,b):
print "CSV"
return a+b
data_type = "CSV"
if data_type == "CSV":
process_data = process_csv
else:
process_data = process_sql
for a in range(3):
for b in range(3):
print process_data(a,b)
# CSV
# 0
# CSV
# 1
# CSV
# 2
# CSV
# 1
# CSV
# 2
# CSV
# 3
# CSV
# 2
# CSV
# 3
# CSV
# 4
您可以尝试编写生成器,从嵌套循环生成值流。这还允许您使用
itertools.islice
简化SQL批处理代码
def my_generator(final):
for comp_name, row in final.items():
for ip_address, sub_row in row.items():
for index, ip_hist in enumerate(sub_row):
yield comp_name, ip_address, index, ip_hist.replace('"', "'")
def output_ip_hist(target, final, stats, table_name, bulk_qty, type = "sql"):
items = my_generator(final)
if type == "sql":
field_names = ",".join(get_field_names(final, table_name))
stats[table_name] = 0
while True:
values = ['("%s", "%s", "%s", "%s")' % i for i in islice(items, bulk_qty)]
if not values:
break
insert_sql_many(target, len(values), table_name, field_names, values, stats)
elif type == "csv":
for comp_name, ip_address, index, hist_item in items:
blob = {
"computer_name": comp_name,
"id": str(index),
"ip_address": ip_address,
"hist_item": hist_item
}
insert_csv(target, blob, stats, table_name)
不过,将两个不同的函数合并成一个函数,封装一个if
station,这有点像是一种反模式
def output_ip_hist_sql(target, final, stats, table_name, bulk_qty):
field_names = ",".join(get_field_names(final, table_name))
stats[table_name] = 0
items = my_generator(final)
while True:
values = ['("%s", "%s", "%s", "%s")' % i for i in islice(items, bulk_qty)]
if not values:
break
insert_sql_many(target, len(values), table_name, field_names, values, stats)
def output_ip_hist_csv(target, final, stats, table_name):
items = my_generator(final)
for comp_name, ip_address, index, hist_item in items:
blob = {
"computer_name": comp_name,
"id": str(index),
"ip_address": ip_address,
"hist_item": hist_item
}
insert_csv(target, blob, stats, table_name)