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Top Questions People Ask About Pandas, NumPy, Matplotlib & Scikit-learn — Answered!

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 Whether you're a beginner or brushing up on your skills, these are the real-world questions Python learners ask most about key libraries in data science. Let’s dive in! 🐍 🐼 Pandas: Data Manipulation Made Easy 1. How do I handle missing data in a DataFrame? df.fillna( 0 ) # Replace NaNs with 0 df.dropna() # Remove rows with NaNs df.isna(). sum () # Count missing values per column 2. How can I merge or join two DataFrames? pd.merge(df1, df2, on= 'id' , how= 'inner' ) # inner, left, right, outer 3. What is the difference between loc[] and iloc[] ? loc[] uses labels (e.g., column names) iloc[] uses integer positions df.loc[ 0 , 'name' ] # label-based df.iloc[ 0 , 1 ] # index-based 4. How do I group data and perform aggregation? df.groupby( 'category' )[ 'sales' ]. sum () 5. How can I convert a column to datetime format? df[ 'date' ] = pd.to_datetime(df[ 'date' ]) ...
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Python Set comprehension - How to Use it Read now

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In python, Set does not allow duplicates, and  you can't modify an existing set with a comprehension. But using the Set comprehension you can create a new Set.


set comprehension


Set Comprehension 


In addition, the comprehension must result in a valid set.  Likewise Dictionary, a set does not allow entries of the same value.


If you try to add values to the set that are already there, it will replace the old one with the new one.

Explained syntax

Set comprehensions using the {} syntax only exist in Python 3. Before that, you'll have to use the set() function to create and work with sets. You might guess, therefore, that one of the best uses of a set is to eliminate duplicates.

In fact, this is one of the most basic forms of set comprehension. Given a list, we can duplicate it as a list with a simple list comprehension like this:

Details of logic

if we change the list comprehension to a set comprehension, we get the same result, but as a set. That means without duplicates.

list_copy = [x for x in original_list]
 

Sample Set comprehension

my_list_with_dupes = [1,2,1,2,3,4,1,2,3,4,5,6,7,1,2,3] 
my_set_without_dupes = {x for x in my_list_with_dupes} 
print(my_set_without_dupes) 

{1, 2, 3, 4, 5, 6, 7}


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