Pandas的常用函数

Title: Pandas的常用函数
Author: Kopei
Created at: 2018-09-17 00:00:00
Updated at: 2025-08-13 18:15:58
Link: https://kopei.github.io/2018/09/16/python-2018-09-17-pandas-common-methods/
License: This work is licensed under <a class="license" target="_blank" rel="noopener" href="https://creativecommons.org/licenses/by-nc-sa/4.0">CC BY-NC-SA 4.0 .

前言

Pandas有一些常用方法, 可以作为回调函数用于其它函数.

pandas.DataFrame.reindex

reindex方法用于把DataFrame按新的索引转化, 同时可选填充空值或者其他方法(如ffill, 按前项填充). 默认情况下, 重新索引过的DataFrame会复制原来DataFrame, 除非索引没有变或者设置copy=False.

>>> frame5 = pd.DataFrame(np.arange(9).reshape((3,3)), index=['a','b','c'], columns=['Ohio','Texas','California'])
>>> frame5
   Ohio  Texas  California
a     0      1           2
b     3      4           5
c     6      7           8
>>> frame5 = frame5.reindex(['a','b','c','d'])
>>> frame5
   Ohio  Texas  California
a   0.0    1.0         2.0
b   3.0    4.0         5.0
c   6.0    7.0         8.0
d   NaN    NaN         NaN

丢弃某些行或列

对于DataFrame, 想要删除某行或列是很方便的, 直接通过drop([])方法可以实现, 默认删除行, 如果需要删除列, 可以设置参数axis=1.

>>> frame5
   Ohio  Texas  California
a   0.0    1.0         2.0
b   3.0    4.0         5.0
c   6.0    7.0         8.0
d   NaN    NaN         NaN
>>> frame5.drop(['a'])
   Ohio  Texas  California
b   3.0    4.0         5.0
c   6.0    7.0         8.0
d   NaN    NaN         NaN
>>> frame5.drop(['Ohio'], axis=1)
   Texas  California
a    1.0         2.0
b    4.0         5.0
c    7.0         8.0
d    NaN         NaN