# 6.10. Numpy Pandas quiz¶

```
import pandas as pd
import numpy as np
```

For the duration of this quiz, assume that pandas has been imported as
`pd`

and numpy as `np`

, as in the cell above.

```
names2000 = pd.read_csv('names/yob2000.txt',names=['name','sex','births'])
```

Next assume that `names2000`

is the result of the above read command.

## 6.10.1. Selecting columns and rows¶

In the next cell, write down what type of Python object `names2000`

is
after the cell above has been executed:

```
[1]:
```

In the next cell, write an expression selecting the `sex`

column of
`names2000`

:

```
[2]:
```

In the next cell wrte an expression that retrieves the fourth through
the sixth row of the `birth`

column of `names2000`

(keeping in mind
that the second row is indexed 1):

```
[3]:
```

## 6.10.2. Selecting multiple columns¶

What if we just want to know the names and the birth counts, but not the
gender? Pandas makes it really easy to select a subset of the columns.
Write an expression that returns the subtable of the `names2000`

dataframe that contains just the `names`

and the `births`

columns:

```
[4]:
```

When you executed the expression that showed you the subtable, it just showed you a summary. Write an expression that just returns the first 18 rows of the subtable:

```
[5]:
```

## 6.10.3. Numpy¶

Assume the following code has been executed:

```
import numpy as np
x = np.array([4,3,1,0])
y =np.arange(5)
z = 2 * x
```

Write expressions in the next cell to retrieve 0 from `x`

, 4 from
`y`

, and 6 from `z`

:

```
[6]:
```

In the next cell, write an expression that generates a 3 by 4 array filled with zeros, and another that generates a 3 by 1 array filled with ones:

```
[7]:
```

In the next cell, write an expression that uses an assignment to a
splice to make all the even values in `a`

be 1. Attention: This can be
done more easily in numpy than it can in normal Python. See if you can
do it the easy way:

```
[ ]: a = np.arange(1,5)
[8]:
```

In the next cell write an expression that produces an array containing result of adding 3 to each of the first 5 integers (1 - 5). There’s a hard way to do this and an easy way. The easy way uses elementwise operations:

```
[9]:
```