Module 4 Graded Quiz: Working with Data in Python :Python for Data Science, AI & Development (IBM Data Analyst Professional Certificate) Answers 2025
1. Question 1
Outcome of:
a = np.array([-1,1])
b = np.array([1,1])
np.dot(a,b)
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❌ array([0,2])
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❌ 1
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❌ array([[-1,-1],[1,1]])
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✅ 0
Explanation:
Dot product = (-1×1) + (1×1) = -1 + 1 = 0.
2. Question 2
First step before matrix multiplication?
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✅ The number of columns in A must equal the number of rows in B.
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❌ Both arrays must be square
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❌ Sum of dimensions must be even
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❌ Arrays must have same shape
Explanation:
Matrix multiplication rule: A (m×n) × B (n×p).
3. Question 3
Output of X.ndim for:
X = np.array([[1,0,1],[2,2,2]])
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❌ 6
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❌ 3
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✅ 2
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❌ 5
Explanation:X is a 2-dimensional array (rows & columns).
4. Question 4
What happens when multiplying a NumPy array by a scalar?
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❌ Only first row multiplied
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❌ Scalar becomes a dimension
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❌ Only diagonal changes
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✅ Each element is multiplied by the scalar value
Explanation:
Scalar multiplication is element-wise.
5. Question 5
Output of:
with open("Example1.txt","r") as file1:
FileContent = file1.readline()
print(FileContent)
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❌ Empty output
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✅ This is line 1
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❌ Full file
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❌ “This”
Explanation:.readline() reads only the first line.
6. Question 6
Advantage of using a with statement?
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✅ It automatically closes the file when the block is exited.
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❌ Improves reading speed
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❌ Enables writing to any file
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❌ Makes file read-only
Explanation:with ensures safe file handling using context managers.
7. Question 7
What happens with "w" mode on an existing file?
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✅ Erases old contents and replaces them with new content
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❌ Raises an error
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❌ File unchanged
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❌ Appends to file
Explanation:w = overwrite mode.
8. Question 8
Difference between "w" and "a" modes?
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❌ binary vs text
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❌ w faster
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✅ “w” overwrites; “a” appends
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❌ w creates new files only
Explanation:
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w= overwrite -
a= append
9. Question 9
Difference between .loc and .iloc in pandas?
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❌ loc = rows, iloc = columns
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❌ loc faster
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❌ loc only single cells
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✅ loc uses labels, iloc uses integer positions
Explanation:
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df.loc["row_label"] -
df.iloc[0]
10. Question 10
How to create a DataFrame from a dictionary?
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❌ pd.dict_to_df
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✅ pd.DataFrame(dictionary)
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❌ pd.from_dict
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❌ pd.create_dataframe
Explanation:
The standard constructor is pd.DataFrame().
🧾 Summary Table
| Q# | Correct Answer | Key Concept |
|---|---|---|
| 1 | 0 | Dot product |
| 2 | Cols(A)=Rows(B) | Matrix multiplication rule |
| 3 | 2 | ndim returns number of dimensions |
| 4 | Element-wise multiply | Scalar × array |
| 5 | “This is line 1” | readline() reads first line |
| 6 | Auto-close file | with statement |
| 7 | Overwrites file | Mode “w” |
| 8 | w = overwrite, a = append | File modes |
| 9 | loc = labels, iloc = integers | Pandas indexing |
| 10 | pd.DataFrame(dict) | Create DataFrame |