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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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3 Best Methods to Read Files in Python

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Read file line by line

Python supports three specific methods to read files- read, readline, readlines. All these you use on files. Each has its unique purpose. Below are the best examples.

3 Methods to read file

  1. read
  2. readline
  3. readlines

Method-1: read

It reads records from file in sequence.

Here, file.txt is sample file with single row.

file.txt


abcdefghijk

file_object.read(2) ==> you will get 'ab'

file_object.read(4)  ===> you will get 'cdef'


Here, the multiple read methods read the data in sequence. The read(x) method will read only the number of characters that mentioned in the read method. Again, if you give multiple read methods then it will read in sequence.


Method-2: readline


It reads the file line by line.

Here, file.txt is a file with single row.

file.txt

abcdefghijk

file_object.readline() ==> you will get 'abcdefghijk'

Here, it reads the file line by line.


Method-3: readlines

It reads all the records at a time.

Here, file.txt is a file with two rows.

file.txt

abcdefghijk
iiiooooooia

file_object.readlines() ==> you will get both the lines.


abcdefghijk
iiiooooooia

Here, it reads all the lines at a time.

Summary

  • I've demonstrated three methods
  • Useful for interviews and projects

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