pandas 在添加新列时返回一个系列而不是 dataframe

Question

I am trying to perform a simple operation of creating a new dataframe from an existing dataframe and also trying to add a new column at the same time. However, pandas returns a series instead of a dataframe.

controls['DESC']=cells1['CEL_DESCRIPTION']

I get the following error for: print(controls.info())

AttributeError: 'Series' object has no attribute 'info'

Answer 1

I use this code and don't get an error:

import pandas as pd

old = pd.DataFrame({'temp_c': [17.0, 25.0]},index=['Portland', 'Berkeley'])
print(old)

new = old.copy().assign(temp_f=lambda x: x.temp_c * 9 / 5 + 32)
print();print(new)

print();print(new.info())

output:

          temp_c
Portland    17.0
Berkeley    25.0


          temp_c  temp_f
Portland    17.0    62.6
Berkeley    25.0    77.0


<class 'pandas.core.frame.DataFrame'>
Index: 2 entries, Portland to Berkeley
Data columns (total 2 columns):
 #   Column  Non-Null Count  Dtype  
---  ------  --------------  -----  
 0   temp_c  2 non-null      float64
 1   temp_f  2 non-null      float64
dtypes: float64(2)
memory usage: 48.0+ bytes
None

EDITED

On edit version I edit code for adding columns name with space like temp c instead of temp_c and temp f instead of temp_f like below:

import pandas as pd

old = pd.DataFrame({'temp c': [17.0, 25.0]},index=['Portland', 'Berkeley'])
print(old)

new = old.copy().assign(**{'temp f': (lambda x: x['temp c'] * 9 / 5 + 32)})

print();print(new)

print();print(new.info())

output:

          temp c
Portland    17.0
Berkeley    25.0

          temp c  temp f
Portland    17.0    62.6
Berkeley    25.0    77.0

<class 'pandas.core.frame.DataFrame'>
Index: 2 entries, Portland to Berkeley
Data columns (total 2 columns):
 #   Column  Non-Null Count  Dtype  
---  ------  --------------  -----  
 0   temp c  2 non-null      float64
 1   temp f  2 non-null      float64
dtypes: float64(2)
memory usage: 48.0+ bytes
None