GroupBy, Merge और Pivot Tables

Pandas groupby और merge क्या है?

Pandas groupby और merge ka matlab hai: groupby summarizes data by category, and merge combines two DataFrames using a common column. Simple words me, ye topic practical Python programs likhne me direct use hota hai.

Is topic ko sirf definition ke liye nahi, balki class-wise summaries jaise real examples ke liye practice karein.

यह क्यों सीखना जरूरी है?

• Ye class-wise summaries me kaam aata hai.
• Ye combining related tables se bhi connected hai.
• Isse aap code ka output aur errors better samajh paate hain.

Important Terms

Syntax / Basic Pattern

Basic idea: pehle data तैयार करें, phir Python logic apply करें, aur finally result display करें.

import pandas as pd
df = pd.DataFrame({
    "Class": ["X", "X", "XI"],
    "Marks": [80, 90, 85]
})
summary = df.groupby("Class")["Marks"].mean()
print(summary)

Complete Example Program

import pandas as pd

df = pd.DataFrame({
    "Class": ["X", "X", "XI"],
    "Marks": [80, 90, 85]
})

summary = df.groupby("Class")["Marks"].mean()
print(summary)

Expected Output

Program Explanation

• import pandas as pd imports ready-made features from a module/library.
• df = pd.DataFrame({ stores a value in df.
• "Class": ["X", "X", "XI"], performs the next step of the program logic.
• "Marks": [80, 90, 85] performs the next step of the program logic.
• }) performs the next step of the program logic.
• summary = df.groupby("Class")["Marks"].mean() stores a value in summary.
• print(summary) displays information or calculated result on the screen.

Practical Uses

• Class-wise summaries.
• Combining related tables.
• Category-wise analysis.

Common Mistakes

• Analysing data before checking missing values, duplicates and data types.
• Changing original data without keeping a clean copy.
• Creating charts without title, labels or explanation.

Practice Tasks

1. Program ko pandas-groupby-merge.py file me type karke run karein.
2. Values change karke output compare karein.
3. class-wise summaries par ek छोटा example banayen.
4. Logic ko apne words me 5 lines me likhein.

सारांश

Pandas groupby and merge ko tab complete maanenge jab aap iska meaning, example, output aur practical use clearly explain kar saken.