In fact this is how the `for` loop works: If we write

```{code-block} python3

:class: no-execute

for x in iterator:

<code block>

```

So now you know how this magical looking syntax works

```{code-block} python3

:class: no-execute

f = open('somefile.txt', 'r')

for line in f:

# do something

Next, we import a module called `amodule`

```{code-block} python3

:class: no-execute

import amodule

```

Complete the following code, and test it using [this csv file](https://raw.githubusercontent.com/QuantEcon/lecture-python-programming/master/source/_static/lecture_specific/python_advanced_features/test_table.csv), which we assume that you've put in your current working directory

```{code-block} python3

:class: no-execute

def column_iterator(target_file, column_number):

"""A generator function for CSV files.

When called with a file name target_file (string) and column number

Suppose we have a text file `numbers.txt` containing the following lines

```{code-block} none

:class: no-execute

prices

3

8