How can I get around declaring an unused variable in a for loop?

Question

If I have a list comprehension (for example) like this:

[\'\' for x in myList]

Effectively making a new list that has an empty string for e

Answer 1

It turns out that using dummy* (starting word is dummy) as the variable name does the same trick as _. _ is a known standard and it would be better to use meaningful variable names. So you can use dummy, dummy1, dummy_anything. By using these variable names PyLint won't complain.

Answer 2

The generator objects don't actually use the variables. So something like

list(('' for x in myList))

should do the trick. Note that x is not defined as a variable outside of the generator comprehension.

Answer 3

Try it, it's simple:

# Use '_' instead of the variable
for _ in range(any_number):
    do_somthing()

Answer 4

_ is a standard placeholder name for ignored members in a for-loop and tuple assignment, e.g.

['' for _ in myList]

[a+d for a, _, _, d, _ in fiveTuples]

BTW your list could be written without list comprehension (assuming you want to make a list of immutable members like strings, integers etc.).

[''] * len(myList)

Answer 5

If you need to name your arguments (in case, for example, when writing mocks that don't use certain arguments that are referenced by name), you can add this shortcut method:

def UnusedArgument(_):
  pass

and then use it like this

def SomeMethod(name_should_remain):
  UnusedArgument(name_should_remain)

Answer 6

You can also prepend a variable name with _ if you prefer giving the variable a human readable name. For example you can use _foo, _foo1, _anything and PyLint won't complain. In a for loop, it would be like:

for _something in range(10):
    do_something_else()

edit: Add example