Using dis to look at the bytecode generated for the two versions: not == 4 0 LOAD_FAST 0 (foo) 3 LOAD_FAST 1 (bar) 6 COMPARE_OP 2 (==) 9 UNARY_NOT 10 RETURN_VALUE != 4 0 LOAD_FAST 0 (foo) 3 LOAD_FAST 1 (bar) 6 COMPARE_OP 3 (!=) 9 RETURN_VALUE The latter has fewer operations, and is therefore … Read more
Angular 1.1.5 added support for ternary operators: {{myVar === “two” ? “it’s true” : “it’s false”}}
Single [] are posix shell compliant condition tests. Double [[]] are an extension to the standard [] and are supported by bash and other shells (e.g. zsh, ksh). They support extra operations (as well as the standard posix operations). For example: || instead of -o and regex matching with =~. A fuller list of differences … Read more
You can use the “pattern-match” operator ~=: if 200 … 299 ~= statusCode { print(“success”) } Or a switch-statement with an expression pattern (which uses the pattern-match operator internally): switch statusCode { case 200 … 299: print(“success”) default: print(“failure”) } Note that ..< denotes a range that omits the upper value, so you probably want … Read more
You may use data.table::fifelse (data.table >= 1.12.3) or dplyr::if_else. data.table::fifelse Unlike ifelse, fifelse preserves the type and class of the inputs. library(data.table) dates <- fifelse(dates == ‘2011-01-01’, dates – 1, dates) str(dates) # Date[1:5], format: “2010-12-31” “2011-01-02” “2011-01-03” “2011-01-04” “2011-01-05” dplyr::if_else From dplyr 0.5.0 release notes: [if_else] have stricter semantics that ifelse(): the true and … Read more
Use ifelse df %>% mutate(g = ifelse(a == 2 | a == 5 | a == 7 | (a == 1 & b == 4), 2, ifelse(a == 0 | a == 1 | a == 4 | a == 3 | c == 4, 3, NA))) Added – if_else: Note that in dplyr 0.5 … Read more
This has to do with operator precedence. if (i = 1 && i == 0) is not if ((i = 1) && (i == 0)) because both && and == have a higher precedence than =. What it really works out to is if (i = (1 && (i == 0))) which assigns the result … Read more
You can choose: if [[ $? -ne 0 ]]; then # -ne: not equal if ! [[ $? -eq 0 ]]; then # -eq: equal if [[ ! $? -eq 0 ]]; then ! inverts the return of the following expression, respectively.
Alternatively to Martijn’s fine answer, you could chain or. This will return the first truthy value, or None if there’s no truthy value: def check_all_conditions(): return check_size() or check_color() or check_tone() or check_flavor() or None Demo: >>> x = [] or 0 or {} or -1 or None >>> x -1 >>> x = [] … Read more
Use the first; it directly tries to check if something is defined in environ. Though the second form works equally well, it’s lacking semantically since you get a value back if it exists and only use it for a comparison. You’re trying to see if something is present in environ, why would you get just … Read more