简体   繁体   English

如何将新列分配给 Pandas 中的现有 DataFrame

[英]How to assign new column to existing DataFrame in pandas

I'm new to pandas.我是熊猫的新手。 I'm trying to add new columns to my existing DataFrame but It's not getting assigned don't know why can anyone explain me what I'm missing this is what i tried我正在尝试将新列添加到我现有的 DataFrame 中,但它没有被分配不知道为什么有人可以解释我缺少什么这是我尝试过的

import pandas as pd
df = pd.DataFrame(data = {"test":["mkt1","mkt2","mkt3"],
                         "test2":["cty1","cty2","cty3"]})
print("Before",df.columns)
df.assign(test3="Hello")
print("After",df.columns)

Output输出

Before Index(['test', 'test2'], dtype='object')
After Index(['test', 'test2'], dtype='object')

Pandas assign method returns a new modified dataframe with a new column, it does not modify it in place. Pandas 的assign方法返回一个带有新列的新修改过的数据框,它不会就地修改它。

import pandas as pd
df = pd.DataFrame(data = {"test":["mkt1","mkt2","mkt3"],
                         "test2":["cty1","cty2","cty3"]})
print("Before",df.columns)
df = df.assign(test3="Hello") # <--- Note the variable reassingment
print("After",df.columns)

声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.

 
粤ICP备18138465号  © 2020-2024 STACKOOM.COM