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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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How to Call SQL Query from Python

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Python's top supported database is MySQL. You can run SQL queries from Python. Here're best examples of how to connect to MYSQL and access MYSQL tables from Python.


Read: How to Print String in Next Line Easily


Here are Steps

  1. Import MySQL connecter
  2. Give user id, password details
  3. Issue SQL query


Python Logic to import MySQL connector


import mysql.connector


Note: If the MySQL connecter not installed in python, you need to install it using the below command.


pip3 install mysql-connector-python --allow-external mysql-connector-python


How to Call SQL Query from Python



Supply user id and Password


conn=mysql.connector.connect(user='root', password='password', host='localhost', database='sakila')



mycursor=conn.cursor()


Issue SQL Query



mycursor.execute("show tables") # you won't see any result. You need to give print.


print(mycursor.fetchall())


mycursor.execute("select * from customer") # you won't see any result. You need to give print.


print(mycursor.fetchall())


This way you can issue SQL queries in Python.


Read: Top 100 Hadoop Interview Questions 1 of 4

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