Discover schema
Before selecting fields dynamically, inspect available labels and compare them with required names.
Pandas · Pipe
df.columns
DataFrame.columns gives access to a DataFrame’s column labels as a pandas Index. Read it to inspect labels and assign a new label sequence to rename the columns.
How it works
df.columns exposes a DataFrame’s column labels as a pandas Index. Read it to inspect labels or use it in selection and alignment workflows; assigning a same-length label sequence replaces the DataFrame’s column names.
Syntax
DataFrame.columnsReturns
pandas.Index — the column labels of the DataFrame.
Key points
df.columnsidentifies the labels along the DataFrame’s column axis.- Use the property to discover a DataFrame’s current column names before selecting or transforming data.
- The property returns a pandas
Index, preserving the column-label axis abstraction. - Column labels participate in selecting data, renaming fields, and aligning DataFrame operations.
Common mistakes
- The result is an Index rather than a regular Python list, so use Index operations or explicitly convert it when an ordinary list is required.
- Treat the returned labels as immutable; rename columns by assigning a new label sequence to
df.columnsinstead of mutating individual Index entries.
Example: Inspect and rename DataFrame columns
import pandas as pd
df = pd.DataFrame({"name": ["Ada", "Linus"], "score": [98, 95]})
print(df.columns)
print(df["score"])
df.columns = ["student", "points"]
print(df)Inspect the column labels, select a column by label, then replace all labels with a new same-length sequence.
When to use it
Rename all columns
Replace the complete set of column names after loading data with inconsistent headers.
Label-aware manipulation
Use column labels when building selections or aligning DataFrame operations.
Interview questions
QWhat does df.columns return?
DataFrame.columns returns the labels for the DataFrame’s columns as a pandas Index. It represents the column names rather than the row index.
Follow-up: How would you obtain a plain Python list? Convert the result explicitly, for example with df.columns.tolist().
QHow can df.columns be used to rename columns?
Use df.columns to inspect the current labels, and assign a new sequence to rename all columns. The replacement labels should correspond one-for-one with the existing columns.
Follow-up: How would you rename only one column? Use a label-mapping operation such as df.rename(columns={old: new}), preserving the other labels.
QHow does df.columns differ from df.index?
Column labels are separate from row labels: df.columns describes the DataFrame’s column axis, while df.index describes its row axis. Both are axis-label objects used by DataFrame operations.
Follow-up: What related attribute exposes both axes? df.axes returns a list representing the DataFrame’s axes.
Related
DataFrame.indexDataFrame.axes