Week 2 Tuesday Discussion
Contents
Week 2 Tuesday Discussion¶
Reminders:
Quiz #1 during the last 20 minutes of discussion today
Homework #1 due tonight by 23:59
Today
Any questions about Homework #1?
Review for Quiz #1
Quiz #1 Review¶
Question 1 ¶
Suppose I have the DataFrame shown below. How could I find the sub-DataFrame where the values in the column “Hello” are greater than 30?
import pandas as pd
df = pd.DataFrame({"Hi": [8,45,14,19,40,3,47,37,39,9],"Hello": [44,48,45,12,9,41,28,4,37,38]})
df
| Hi | Hello | |
|---|---|---|
| 0 | 8 | 44 |
| 1 | 45 | 48 |
| 2 | 14 | 45 |
| 3 | 19 | 12 |
| 4 | 40 | 9 |
| 5 | 3 | 41 |
| 6 | 47 | 28 |
| 7 | 37 | 4 |
| 8 | 39 | 37 |
| 9 | 9 | 38 |
[c for c in df.columns if df.loc[1,c] > 10]
['Hi', 'Hello']
df["Hello"] > 30
0 True
1 True
2 True
3 False
4 False
5 True
6 False
7 False
8 True
9 True
Name: Hello, dtype: bool
df2 = df[df["Hello"] > 30]
df2
| Hi | Hello | |
|---|---|---|
| 0 | 8 | 44 |
| 1 | 45 | 48 |
| 2 | 14 | 45 |
| 5 | 3 | 41 |
| 8 | 39 | 37 |
| 9 | 9 | 38 |
Question 2 ¶
Briefly describe the difference between iloc and loc. Then, using list comprehension, find all the rows in df where the corresponding value in the column “Hi” is greater than 10 using iloc and then again using loc.
iloc is used for integer-based indexing (starts at 0); you can remember this by thinking that “i” stands for “integer”.
loc is used for label-based indexing.
iloc is used for integer-based indexing (starting at 0), while loc is label-based indexing. The solution to the second half of this question gives an example of how both can work for the same question.
[r for r in df.index if df.loc[r,"Hi"] > 10]
[1, 2, 3, 4, 6, 7, 8]
[r for r in range(len(df)) if df.iloc[r,0] > 10]
[1, 2, 3, 4, 6, 7, 8]
#tuple
df.shape
(10, 2)
df.index
RangeIndex(start=0, stop=10, step=1)
[r for r in df.index if df.loc[r,"Hi"] > 10]
[1, 2, 3, 4, 6, 7, 8]
df.shape[0]
10
[r for r in range(len(df)) if df.iloc[r,0] > 10]
[1, 2, 3, 4, 6, 7, 8]
[r for r in range(len(df)) if df.iloc[r,0] > 10]
[1, 2, 3, 4, 6, 7, 8]
Question 3 ¶
How could you make the following output using a for-loop and f-strings?
for i in range(0,13,3):
print(f"The square of {i} is {i**2}.")
The square of 0 is 0.
The square of 3 is 9.
The square of 6 is 36.
The square of 9 is 81.
The square of 12 is 144.
for i in range(0,13,3):
print(f"The square of {i} is {i**2}.")
The square of 0 is 0.
The square of 3 is 9.
The square of 6 is 36.
The square of 9 is 81.
The square of 12 is 144.