列表推导式使用疑问：复杂循环转换失败及转换可行性咨询

我尝试用列表推导式优化代码，已经成功把下面的简单循环转换成列表推导式：

# 旧写法
loaded_sounds = []
for i in assetList_text:
    if i.startswith("loaded_sound"):
        loaded_sounds.append(i.split(',')[1])

# 新写法
loaded_sounds = [i.split(',')[1] for i in assetList_text if i.startswith("loaded_sound")]

但在转换带有两个条件且包含去重逻辑的循环时，结果不符合预期：

原循环执行后输出长度为6：

gsc_files = []
for i in assetList_text:
    if ".gsc" in i:
        d = i.split(',')[-1].replace("\n", "")
        if d not in gsc_files:
            gsc_files.append(d)

而我写的对应列表推导式执行后输出长度为0：

gsc_files = [i.split(',')[-1].replace("\n", "") for i in assetList_text if ".gsc" in i if i.split(',')[-1].replace("\n", "") not in gsc_files]

我不知道问题出在哪里。另外，我想了解列表推导式的适用范围，请问下面两个循环能不能转换为列表推导式？

[1] 嵌套循环 #

weapon_files = []
x = join(f"{WAW_ROOT_DIR}/raw/weapons/sp")
for path, subdirs, files in walk(x):
    for fileName in files:
        content = join(x, fileName)
        if content not in weapon_files:
            weapon_files.append(f"{WAW_ROOT_DIR}/raw/weapons/sp/{fileName}")

[2] 多分支条件循环 #

gsc_files_dir = []
for path in gsc_files:
    if f"{CURRENT_SELECTED_MOD.lower()}" in path:
        dir = join(f"{WAW_ROOT_DIR}/mods/{CURRENT_SELECTED_MOD}/{path}")
        gsc_files_dir.append(dir)
    elif os.path.exists(f"{WAW_ROOT_DIR}/mods/{CURRENT_SELECTED_MOD}/{path}"):
        dir = join(f"{WAW_ROOT_DIR}/mods/{CURRENT_SELECTED_MOD}/{path}")
        gsc_files_dir.append(dir)
    else:
        dir = join(f"{WAW_ROOT_DIR}/raw/{path}")
        gsc_files_dir.append(dir)

附：数据示例 #

assetList_text是读取自多个CSV文件的3000+行数据，部分含.gsc的行示例如下：

fx,weapon/shellejects/fx_smk_weapon_shell_eject
fx,weapon/shellejects/fx_smk_weapon_shell_emit
...
rawfile,maps/free_city.gsc
...

内容的提问来源于stack exchange，提问作者Phil Gibson