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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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PL/SQL Sample code and error handling mechanism

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SAMPLE PL/SQL



CREATE TABLE dummy


( dummy_value       VARCHAR2(1));
DECLARE
  -- Define local variable.
  my_string VARCHAR2(1) := ' ';
  my_number NUMBER;
BEGIN
  -- Select a white space into a local variable.
  SELECT ' ' INTO my_string FROM dummy;
  -- Attempt to assign a single white space to a number.
  my_number := TO_NUMBER(my_string);
EXCEPTION
 WHEN no_data_found THEN
   dbms_output.put_line('SELECT-INTO'||CHR(10)||SQLERRM);
END;
/







Output and Error:

The program returns the following output, which illustrates formatting user- defined exceptions. 





The CHR(10) inserts a line return and provides a clean break between the program's SQLCODE and SQLERRM messages:







RAISE my_error SQLCODE [1] 



SQLERRM [User-Defined Exception]







































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