Nameerror: name 'col' is not defined

Nameerror: name ‘col’ is not defined

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Are you dealing with the Python nameerror: name ‘col’ is not defined while working in Pyspark?

If you’re struggling to fix the name ‘col’ is not defined, keep on reading!

This article discusses what this error means and will explore how to fix this error simply and effectively.

What is “nameerror name ‘col’ is not defined”?

The error message nameerror: name ‘col’ is not defined occurs when you are using the variable or function “col” without importing it first.

In simple words, this error message occurs when the “col” function is not imported or defined correctly.

In addition to that, it occurs when the PySpark interpreter cannot find the “col” function.

The “col” function is used to access a column in a PySpark dataframe.

What are the root causes of “nameerror: name ‘col’ is not defined”?

This error can occur because of several factors that includes the following:

❌ Missing import statement.

❌ Incorrect installation of the PySpark package.

❌Typo in the function name.

How to fix “nameerror: name ‘col’ is not defined”?

To fix this error, ensure that you have imported the “col” function correctly. 

If you’re using PySpark, you can import the “col” function from pyspark.sql.functions by adding the line from pyspark.sql.functions import col at the beginning of your Python script

Here are the following solutions which you can use to fix this error.

Solution 1: Import “col” function

You have to import the “col” function from pyspark.sql.functions to use its function.

For example:

✅ from pyspark.sql.functions import col

Solution 2: Use alias for the col function

If you want to use another name for the “col” function, you can import it with an alias by using the following line at the top or beginning of your script.

For example:

✅ from pyspark.sql.functions import col as column

This solution allows you to use the column function in your code instead of “col.”

3. Import all pyspark functions directly

You can also import all pyspark functions directly. However, import * is generally discouraged as it can lead you to unknown imports or overwrites.

For example:

from pyspark.sql.functions import *


add your code here>>


This line calls the col function 👇
col('my_column')

On the other hand, you can also use an alias in order to solve function shadowing.

For example:

from pyspark.sql import functions as f

add your code here>>

This line calls the col function 👇
f.col('my_column')

4. Use the fully qualified name for the col function

When you prefer not to import the “col” function, you can use its fully qualified name by using the following line at the top or beginning of your script.

For example:

✅ import pyspark.sql.functions as F

After you import the “col” function, you can use the function in your code by calling it as F.col.

For example:

✅ df.select(F.col("column_name"))

Conclusion

In conclusion, the error message nameerror: name ‘col’ is not defined occurs when you are using the variable or function “col” without importing it first.

This article discusses what this error is all about and already provides solutions to help you fix this error.

You could also check out other “nameerror” articles that may help you in the future if you encounter them.

We are hoping that this article helps you fix the error. Thank you for reading itsourcecoders 😊

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