Pandas DataFrame sem() Method
Example
Return the standard error of the mean for each column:
    import pandas as pd
data = [[10, 18, 11], [13, 15, 8], [9, 20, 3]]
    
df = pd.DataFrame(data)
print(df.sem())
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Definition and Usage
The sem() method calculates the standard 
error of the mean for each column.
By specifying the column axis (axis='columns'), the 
sem() 
method searches column-wise and returns the standard error of the mean for each row.
Syntax
  
    dataframe.sem(axis, skipna, level, ddof, numeric_only)
  
Parameters
The parameters are keyword arguments.
| Parameter | Value | Description | 
|---|---|---|
| axis | 0 | 
    Optional, Which axis to check, default 0. | 
| skip_na | True | 
    Optional, default True. Set to False if the result should NOT skip NULL values | 
| level | Number level name  | 
    Optional, default None. Specifies which level ( in a hierarchical multi index) to check along | 
| ddof | Number | 
    Optional, default 1. Specifies the Delta Degrees of Freedom | 
| numeric_only | None | 
    Optional. Specifies whether to only check numeric values. Default None | 
Return Value
A Series with the standard deviations.
If the level argument is specified, this method will return a DataFrame object.
This function does NOT make changes to the original DataFrame object.