python关于一维数据转二维数据补足缺少数据为0的问题

请问如何利用python将1-1.csv转换为2.csv这样的格式，即按照顺序，每一组标签为一组，数据缺失补0。学艺不精，弄了很久都没弄出来。希望各位能够不吝赐教

懒得编制测试文件，代码未经测试，请题主自测吧。

with open('1-1.csv', 'r') as fp:
    data_raw = [line.strip().split(',') for line in fp.readlines()]

keys = list(set([item[0] for item in data_raw])) # 键去重
group = list()
values = ['0' for i in range(len(keys))]

with open('2.csv', 'w') as fp:
    for item in data_raw:
        if item[0] in group:
            line = ','.join(values)
            fp.write('%s\n'%line)
            
            group = list()
            values = ['0' for i in range(len(keys))]
        
        group.append(item[0])
        values[keys.index(item[0])] = item[1]

    if group:
        line = ','.join(values)
        fp.write('%s\n'%line)