You can find out how to replace substring in a column of Pandas DataFrame using DataFrame.replace()
with lambda
functions. In this article, I will explain how to replace the substring in the DataFrame column with multiple examples.
Key Points –
- Replace a substring with another substring in Pandas.
- Replace a pattern of a substring with another substring using regular expression.
- Specify the column containing the target substrings within the DataFrame.
- Use the
str.replace()
method in Pandas to replace substrings within DataFrame columns. - Provide the substring to be replaced and the replacement string as arguments to the
str.replace()
method.
Related: You can replace the string in Pandas DataFrame.
Quick Examples to Replace Substring
If you are in a hurry below are some quick examples of how to replace a substring in a column of pandas DataFrame.
# Quick examples to replace substring
# Example 1: Replace substring
df2 = df.replace('Py','Python with ', regex=True)
# Example 2: Replace substring
df2 = df.replace('Py','Python with ', regex=True)
# Example 3: Replace multiple substrings
df2 = df.replace({'Courses': 'Py', 'Duration': 'days'},
{'Courses': 'Python with', 'Duration': ' Days'}, regex=True)
# Example 4: Replace pattern of Substring using regular expression.
df2=df.replace(regex=['Language'],value='Lang')
# Example 5: Using str.replace()
df['Courses'] = df['Courses'].str.replace('Language','Lang')
# Example 6: Replace SubString using apply() function with lambda.
df2 = df.apply(lambda x: x.replace(
{'Py':'Python with', 'Language':'Lang'},
regex=True))
Now, Let’s create a pandas DataFrame with a few rows and columns, execute these examples, and validate the results. Our DataFrame contains column names Courses
, Fee
and Duration
.
# Create a pandas DataFrame.
import pandas as pd
import numpy as np
technologies= {
'Courses':["Spark","PySpark","Spark","Java Language","PySpark","PHP Language"],
'Fee' :[22000,25000,23000,24000,26000,27000],
'Duration':['30days','50days','30days','60days','35days','30days']
}
df = pd.DataFrame(technologies)
print("Create DataFrame:\n", df)
Yields below output.
Replace Substring Using replace() Method
You can replace the substring of the Pandas DataFrame column by using the DataFrame.replace() method. This method by default finds the exact string match and replaces it with the specified value. Use regex=True
to replace the substring.
# Replace substring
df2 = df.replace('Py','Python with ', regex=True)
print("After replacing the substring with another substring:\n", df2)
Yields below output. The above example replaced the substring value Py
with Python
on column Courses
.
This method returns a new DataFrame after replacing the substring. Use inplace=True
to replace on existing DataFrame object.
Replace Multiple Substrings
Alternatively, you can apply this method to multiple string columns in a DataFrame and allows you to replace occurrences of substrings with other substrings. Let’s see how to replace substring on multiple columns, to do this I will be using dict with column names and values to replace.
# Replace multiple substrings
df2 = df.replace({'Courses': 'Py', 'Duration': 'days'},
{'Courses': 'Python with', 'Duration': ' Days'}, regex=True)
print("After replacing the multiple substrings:\n", df2)
Yields below output.
# Output:
# After replacing the multiple substrings:
Courses Fee Duration
0 Spark 22000 30 Days
1 Python withSpark 25000 50 Days
2 Spark 23000 30 Days
3 Java Language 24000 60 Days
4 Python withSpark 26000 35 Days
5 PHP Language 27000 30 Days
Replace Pattern of Substring Using Regular Expression
To replace a pattern of substring using regular expression in Python, you can utilize the str.replace()
method with the regex=True
parameter in pandas.
# Replace pattern of Substring using regular expression.
df2=df.replace(regex=['Language'],value='Lang')
print("After replacing the substring:\n", df2)
This code will replace the substring Language
with Lang
in the Courses
column of the DataFrame using regular expressions. The regex=True
parameter enables regular expression matching in the replace()
method. This example yields the below output.
# Output:
# After replacing the substring:
Courses Fee Duration
0 Spark 22000 30days
1 PySpark 25000 50days
2 Spark 23000 30days
3 Java Lang 24000 60days
4 PySpark 26000 35days
5 PHP Lang 27000 30days
By using str.replace() on DataFrame
Alternatively, you can use str.replace()
to replace a substring, repalce()
looks for exact matches unless you pass a regex pattern and param regex=True
.
# By using str.replace()
df['Courses'] = df['Courses'].str.replace('Language','Lang')
print("After replacing the substring:\n", df)
Yields the same output as above. Note that this replaces the value on the Courses
column in the existing DataFrame object.
Replace Substring Using apply() Function with Lambda
In this section, You can find out how to replace the substring using DataFrame.apply() and lambda
function. The apply() method allows you to apply a function along with one of the axes of the DataFrame. The below example replaces multiple substring’s.
# Replace SubString using apply() function with lambda.
df2 = df.apply(lambda x: x.replace({'Py':'Python with', 'Language':'Lang'}, regex=True))
print(df2)
Yields below output.
# Output:
Courses Fee Duration
0 Spark 22000 30days
1 Python withSpark 25000 50days
2 Spark 23000 30days
3 Java Lang 24000 60days
4 Python withSpark 26000 35days
5 PHP Lang 27000 30days
Complete Example of pandas Replace Substring
# Create a pandas DataFrame.
import pandas as pd
import numpy as np
technologies= {
'Courses':["Spark","PySpark","Spark","Java Language","PySpark","PHP Language"],
'Fee' :[22000,25000,23000,24000,26000,27000],
'Duration':['30days','50days','30days','60days','35days','30days']
}
df = pd.DataFrame(technologies)
print(df)
# Replace substring
df2 = df.replace('Py','Python with ', regex=True)
print(df2)
# Replace substring
df2 = df.replace('Py','Python with ', regex=True)
print(df2)
# Replace multiple substrings
df2 = df.replace({'Courses': 'Py', 'Duration': 'days'},
{'Courses': 'Python with', 'Duration': ' Days'}, regex=True)
print(df2)
# Replace pattern of Substring using regular expression.
df2=df.replace(regex=['Language'],value='Lang')
print(df2)
# Using str.replace()
df['Courses'] = df['Courses'].str.replace('Language','Lang')
print(df)
# Replace SubString using apply() function with lambda.
df2 = df.apply(lambda x: x.replace(
{'Py':'Python with', 'Language':'Lang'},
regex=True))
print(df2)
FAQ on Pandas Replace substring in DataFrame
To replace a specific substring in a DataFrame column with another substring, you can use the str.replace()
method in pandas.
If you need more flexibility or want to use regular expressions, you can set the regex
parameter to True
.
You can replace substrings conditionally based on their values using pandas’ str.replace()
method along with conditional statements.
It’s possible to replace substrings across the entire DataFrame using the replace()
method in pandas.
Conclusion
In this article, I have explained how to replace the substring of pandas DataFrame by using replace()
with lambda
functions with examples.
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