select to_char(date_published, 'yyyymm') yo from blog group by yo;

In[3]: year_field = db.func.extract('year', ArticleModel.date_published)

In[4]: month_field = db.func.extract('month', ArticleModel.date_published)

In[5]: yonth_field = year_field *100+ month_field

In[6]:print db.session.query(yonth_field.label('yonth'), db.func.count(1)).group_by('yonth')

SELECT EXTRACT(year FROM article_meta.date_published)*:param_1 + EXTRACT(month FROM article_meta.date_published)AS yonth, count(:param_2)AS count_1 
FROM article_meta JOIN article ON article_meta.id = article.id GROUPBY yonth

yonth = db.func.to_char(ArticleModel.date_published,'yyyymm').label('yonth')
archive_list =(db.session.query(yonth,                                 
    db.func.count(1)).group_by('yonth').all())