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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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5 Python File Modes You Need

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Here're top five Python file modes explained. The purpose is to open, read, write the files. There are occasions you need to deal with data, which is present in the files. You need to give correct file-modes to handle the files in Python.


Python file modes crucial to handle the files. Here is the list of file modes to use correctly in your program.
Python file open modes

5 Python File Modes You Need


Here's an example code how to you can use file mode:

  
filename = input('Enter a filename : ')
f1 = open(filename, 'mode')


1- Python File mode w 


To open the file for writing, you need 'w' mode. The beauty of this is If the file does not exist, it creates one. This mode's purpose is to write the file. If you try to read, you will get an error.



2- Python File mode w+


To Open the file for Reading and Writing, you need 'w+' mode. For instance, you used w+, you have tried to read the file - after writing, it displays blank. The reason is after writing cursor position will point at the end of the file.


3- Python File mode a


It appends the records at the end of the existing file. The file must exist to use this mode.


4- Python File mode r


To open a file in read-only mode. If the file does not exist, it throws an error.


5- Python File mode r+


Both read and write. When you write the data to the file, it writes at the end. Now, the cursor is at the end of the file. When you perform read, it gives blank.


In the 'r+' mode, if the file does not exist, and if you try to read, which gives an error.


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