使用Python，我编写了以下脚本来索引csv.reader中的一行，并将其与前一行的相关值进行比较：
source = open('sourcefile')
reader = csv.reader(source)
with open('targetfile','w') as f:
for row in reader:
if row[1] == "NA" and row[2] == "NA":
prevrow = row
line = row
writer = csv.writer(f)
writer.writerow(line)
else:
while row[1] == prevrow[1]:
if row[1] == prevrow[3]:
cumbid = cumbid + row[2]
line = row[0] + "," + row[1] + "," + cumbid + "," + prevrow[3] + "," + prevrow[4] + "," + str(int(float(prevrow[5]))-int(float(cumbid))) + "," + prevrow[6] + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
elif row[1] == prevrow[4]:
cumask = cumask + row[2]
line = row[0] + "," + row[1] + "," + cumask + "," + prevrow[3] + "," + prevrow[4] + "," + prevrow[5] + "," + str(int(float(prevrow[6]))-int(float(cumask))) + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
else:
if row[1] == prevrow[3] and row[2] < prevrow[5]:
cumbid = row[2]
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[3] + "," + prevrow[4] + "," + str(int(float(prevrow[5]))-int(float(row[2]))) + "," + prevrow[6] + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
print prevrow
print prevrow[0]+ " " + prevrow[1]+ " " + prevrow[2]+ " " + prevrow[3]+ " " + prevrow[4]+ " " + prevrow[5]+ " " + prevrow[6]
writer = csv.writer(f)
writer.writerow(line.split())
elif row[1] == prevrow[4] and row[2] < prevrow[6]:
cumask = row[2]
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[3] + "," + prevrow[4] + "," + prevrow[5] + "," + str(int(float(prevrow[6]))-int(float(row[2]))) + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
print prevrow
print prevrow[0]+ " " + prevrow[1]+ " " + prevrow[2]+ " " + prevrow[3]+ " " + prevrow[4]+ " " + prevrow[5]+ " " + prevrow[6]
writer = csv.writer(f)
writer.writerow(line.split())
elif row[1] == prevrow[3] and row[2] == prevrow[5] :
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[7] + "," + prevrow[4] + "," + prevrow[8] + "," + prevrow[6] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[9] + "," + prevrow[10] + "," + "," + "," + "," + "," + "," + "," + ","
prevrow = line
print prevrow
print prevrow[0]+ " " + prevrow[1]+ " " + prevrow[2]+ " " + prevrow[3]+ " " + prevrow[4]+ " " + prevrow[5]+ " " + prevrow[6]
writer = csv.writer(f)
writer.writerow(line.split())
elif row[1] == prevrow[4] and row[2] == prevrow[6]: #the trade was on the offer and took it all out--we have to refer to the 2nd level of the book
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[3] + "," + prevrow[9] + "," + prevrow[5] + "," + prevrow[10] + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[13] + "," + prevrow[14] + "," + "," + "," + "," + "," + "," + "," + ","
prevrow = line
print prevrow
print prevrow[0]+ " " + prevrow[1]+ " " + prevrow[2]+ " " + prevrow[3]+ " " + prevrow[4]+ " " + prevrow[5]+ " " + prevrow[6]
writer = csv.writer(f)
writer.writerow(line.split())
elif row[1] == prevrow[1] and row[1] == prevrow[3] : #trade was on the bid, and the prev row was also a trade--decrement bid size
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[3] + "," + prevrow[4] + "," + str(int(float(prevrow[5]))-int(float(row[2]))) + "," + prevrow[6] + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
writer = csv.writer(f)
writer.writerow(line.split())
elif row[1] == prevrow[1] and row[1] == prevrow[4] : #trade was on the offer, and the prev row was also a trade--decrement ask size
line = row[0] + "," + row[1] + "," + row[2] + "," + prevrow[3] + "," + prevrow[4] + "," + prevrow[5] + "," + str(int(float(prevrow[6]))-int(float(row[2]))) + "," + prevrow[7] + "," + prevrow[8] + "," + prevrow[9] + "," + prevrow[10] + "," + prevrow[11] + "," + prevrow[12] + "," + prevrow[13] + "," + prevrow[14] + "," + ","
prevrow = line
writer = csv.writer(f)
writer.writerow(line.split())
但是，这些后续行会生成以下内容：
print prevrow
print prevrow[0]+ " " + prevrow[1]+ " " + prevrow[2]+ " " + prevrow[3]+ " " + prevrow[4]+ " " + prevrow[5]+ " " + prevrow[6]
20100628000120702,12392.0,1.0,12392.0,12393.0,5.0
2 0 1 0 0 6 2
我希望两行输出都相同，所以像row [1] == prevrow [1]这样的比较会将12392.0与前一行中的第二项（12392.0）进行比较而不是第二个字符。行（0）。所以，我的问题是，prevrow已成为一个字符列表，当我试图按照我可以在行中索引项目的方式对项目进行索引时，我似乎得到了列表中字符的索引。
如何保存当前的“行”并保留其上下文？
答案 0 :(得分：0)
使用tee创建两个虚拟迭代器，递增一个，然后压缩它们，以获得一系列（lastrow，currentrow）元组。 （请参阅itertools documentation中的pairwise食谱。）
然后你可以写：
for prevrow,row in pairwise(reader):
... etc ...
答案 1 :(得分：0)
您正在line中构建字符串并将其存储在prevrow中;改为存储一个列表：
line = row[:2] + [cumbid] + prevrow[3:5] + [str(int(float(prevrow[5])) - int(float(cumbid)))] + prevrow[6:15]