Multiple index variables in PHP foreach loop
to achieve just that result you could do foreach (array_combine($courses, $sections) as $course => $section) but that only works for two arrays
loops
Updating a value in a pandas dataframe in an iterrows loop
The rows you get back from iterrows are copies that are no longer connected to the original data frame, so edits don’t change your dataframe. Thankfully, because each item you get back from iterrows contains the current index, you can use that to access and edit the relevant row of the dataframe: for index, row … Read more
Is it possible to make a `for` loop without an iterator variable? (How can I make make code loop a set number of times?)
Off the top of my head, no. I think the best you could do is something like this: def loop(f,n): for i in xrange(n): f() loop(lambda: <insert expression here>, 5) But I think you can just live with the extra i variable. Here is the option to use the _ variable, which in reality, is … Read more
How can I avoid “RuntimeError: dictionary changed size during iteration” error?
In Python 3.x and 2.x you can use use list to force a copy of the keys to be made: for i in list(d): In Python 2.x calling keys made a copy of the keys that you could iterate over while modifying the dict: for i in d.keys(): But note that in Python 3.x this … Read more
Iterate through adjacent pairs of items in a Python list [duplicate]
You can zip the list with itself sans the first element: a = [5, 7, 11, 4, 5] for previous, current in zip(a, a[1:]): print(previous, current) This works even if your list has no elements or only 1 element (in which case zip returns an empty iterable and the code in the for loop never … Read more
Bash scripting, multiple conditions in while loop
The correct options are (in increasing order of recommendation): # Single POSIX test command with -o operator (not recommended anymore). # Quotes strongly recommended to guard against empty or undefined variables. while [ “$stats” -gt 300 -o “$stats” -eq 0 ] # Two POSIX test commands joined in a list with ||. # Quotes strongly … Read more
Extract list of attributes from list of objects in python
attrs = [o.attr for o in objs] was the right code for making a list like the one you describe. Don’t try to subclass list for this. Is there something you did not like about that snippet?
Breaking loop when “warnings()” appear in R
You can turn warnings into errors with: options(warn=2) Unlike warnings, errors will interrupt the loop. Nicely, R will also report to you that these particular errors were converted from warnings. j <- function() { for (i in 1:3) { cat(i, “\n”) as.numeric(c(“1”, “NA”)) }} # warn = 0 (default) — warnings as warnings! j() # … Read more
Check for null in foreach loop
Just as a slight cosmetic addition to Rune’s suggestion, you could create your own extension method: public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> source) { return source ?? Enumerable.Empty<T>(); } Then you can write: foreach (var header in file.Headers.OrEmptyIfNull()) { } Change the name according to taste 🙂
Is there a “do … until” in Python? [duplicate]
There is no do-while loop in Python. This is a similar construct, taken from the link above. while True: do_something() if condition(): break