提取文档中每一行第一个空格前的内容作为关键字

if __name__ == '__main__':

    name = './data/train.txt'
    with open(name, 'r', encoding='utf-8') as f:
        lines = f.readlines()#获取所有行
        sum = 0
        list = []
        for line in lines:#第i行
            #找到第一个空格
            for j in range(len(line)):
                if line[j].isspace() == True:
                    a = line[:j]
                    if a not in list:
                        list.append(a)
                        sum += 1
                    break
        print(list)