排序

# 排序1 - 按值排序 .sort_values
# 同样适用于Series

df1 = pd.DataFrame(np.random.rand(16).reshape(4,4)*100,
                   columns = ['a','b','c','d'])
print(df1)
print(df1.sort_values(['a'], ascending = True))  # 升序
print(df1.sort_values(['a'], ascending = False))  # 降序
print('------')
# ascending参数：设置升序降序，默认升序
# 单列排序

df2 = pd.DataFrame({'a':[1,1,1,1,2,2,2,2],
                  'b':list(range(8)),
                  'c':list(range(8,0,-1))})
print(df2)
print(df2.sort_values(['a','c']))
# 多列排序，按列顺序排序
# 注意inplace参数

# 排序2 - 索引排序 .sort_index

df1 = pd.DataFrame(np.random.rand(16).reshape(4,4)*100,
                  index = [5,4,3,2],
                   columns = ['a','b','c','d'])
df2 = pd.DataFrame(np.random.rand(16).reshape(4,4)*100,
                  index = ['h','s','x','g'],
                   columns = ['a','b','c','d'])
print(df1)
print(df1.sort_index())
print(df2)
print(df2.sort_index())
# 按照index排序
# 默认 ascending=True, inplace=False