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Pandas Series.str.contains() - Python

Last Updated : 13 Jan, 2026

The Series.str.contains() method is used to check whether each string value in a Pandas Series contains a given substring or pattern. It returns a Boolean Series (True/False) and is mainly used for filtering, searching, or flagging text data based on conditions.

This example checks whether each city name contains the substring "is".


Output
0 True
1 False
2 True
dtype: bool

Explanation:

  • str.contains('is') checks each value for "is"
  • Returns True where the substring is found

Syntax

Series.str.contains(pat, case=True, flags=0, na=None, regex=True)

Parameters:

  • pat: Substring or regex pattern to search
  • case: Case-sensitive match (True by default)
  • flags: Regex flags (example: re.IGNORECASE)
  • na: Value to use for missing data
  • regex: Treat pat as regex if True

Returns: A Boolean Series or Index

Examples

Example 1: This example uses a regex pattern to find names where "i" is followed by a lowercase letter.


Output
0 True
1 True
2 True
3 False
dtype: bool

Explanation: i[a-z] matches "ik" and "im" patterns in the strings

Example 2: This example performs a case-insensitive match to find "grape" in mixed-case text.


Output
0 False
1 True
2 False
dtype: bool

Explanation: flags=re.IGNORECASE allows matching "GRAPE" with "grape"

Example 3: This example shows how Series.str.contains() behaves when the Series contains missing values and how to handle them using the na parameter.


Output
0 True
1 False
2 False
3 True
dtype: bool

Explanation:

  • str.contains('Py') checks for "Py" in each string
  • na=False ensures missing values (None) are treated as False instead of returning NaN
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