如何用Python Pandas获取首元素含'|'的DataFrame列

To find columns where the first element contains a |, you can use a list comprehension that checks each column's initial value:

import pandas as pd

# Your sample DataFrame
df = pd.DataFrame({'A': ['ex1|context1', 1, 'ex3|context3', 3], 'B': [5, 'ex2|context2', 6, 'data']})

# Get columns where first element is a string containing '|'
matching_columns = [col for col in df.columns 
                    if isinstance(df[col].iloc[0], str) and '|' in df[col].iloc[0]]

print(matching_columns)  # Output: ['A']

Explanation: #

• Iterate over columns: We loop through each column name in df.columns.
• Check element type: First, we verify the first element (df[col].iloc[0]) is a string using isinstance()—this prevents errors when checking for | in non-string values (like integers in your sample).
• Check for pipe character: If the element is a string, we then check if '|' is present in it.
• Collect results: Columns that meet both conditions are added to the matching_columns list.

If you want to extract just those columns from your DataFrame, you can do:

filtered_df = df[matching_columns]

内容的提问来源于stack exchange，提问作者alex