<p>I have a list of tuples eg. [{1,40},{2,45},{3,54}....{7,23}] where 1...7 are days of the week (calculated by finding calendar:day_of_the_week()). So now I want to change the list to [{Mon,40},{Tue,45},{Wed,54}...{Sun,23}]. Is there an easier way to do it than lists:keyreplace?</p>

Simple. Use map and a handy tool from the httpd module.
```
```
lists:map(fun({A,B}) -> {httpd_util:day(A),B} end, [{1,40},{2,45},{3,54},{7,23}]).
```
```