Impressions are available in
many different reports. You can extract only the required data from a report by creating date filters as shown in
this example (same example is available in
other client libraries as well). Also, you can
segment a report based on the segmentation fields available in a report. In general, you can segment most reports on Date and DayOfWeek (Sunday, Monday etc.). To segment a report via the API, all you need to do is to add the segmentation field (i.e. Date etc.) to the report. However, please note that data available via AdWords API cannot be considered real time i.e. you might have to wait for sometime before the most recent data becomes available. For exact timelines please refer to
this guide.