default-value

问题 Here I have to set the default value if the user will enter the value from the keyboard. Here is the code that user can enter value: input = int(raw_input("Enter the inputs : ")) Here the value will be assigned to a variable input after entering the value and hitting Enter . Is there any method that if we don't enter the value and directly hit the Enter key, the variable will be directly assigned to a default value, say as input = 0.025 ? 回答1: input = int(raw_input("Enter the inputs : ") or

问题 I'm confused about some basic theory in C programing: What are the default values for variables of different datatypes? Example: If I declare as follows what may be the result according to standard C manual which is documented by legend Dr. Dennis Ritchie? int x; printf("%d",x); I knows that some GCC compilers will print 0 and some print garbage values. It depends on compiler. Please give me the unique answer as per Dennis Ritchie C programing documentation. Same as above, please give me

问题 In MS-SQL Server, is it possible to pass a parameter to a DEFAULT function, or somehow base the DEFAULT value on the values inserted in the record? You can assign a function as a DEFAULT value for a column in MS-SQL Server. Using this, I'm trying to achieve the following. For a table with study ids and patient ids, I want to automatically assign a new patient number within that study. CREATE TABLE [dbo].[PATIENT_STUDY]( [PatientStudyID] [int] IDENTITY(1,1) NOT NULL, [PatientID] [int] NOT NULL

问题 Suppose I have a Python function foo which takes a default argument, where that default is set to some global variable. If I now change that global variable before calling the function, the default argument is still set to the original value of that global variable. For example: x = 1 def foo(a=x): print a x = 2 foo() This prints 1 , instead of 2 . How should I be writing my code, so that I can change this global variable, and have it update this default argument? 回答1: A default variable is

问题 And can I therefore safely refactor all instances of class Blah { // ... private $foo = null; // ... } to class Blah { // ... private $foo; // ... } ? 回答1: Simple answer, yes. See http://php.net/manual/en/language.types.null.php The special NULL value represents a variable with no value. NULL is the only possible value of type null. You can easily test by performing a var_dump() on the property and you will see both instances it will be NULL class Blah1 { private $foo; function test() { var

问题 And can I therefore safely refactor all instances of class Blah { // ... private $foo = null; // ... } to class Blah { // ... private $foo; // ... } ? 回答1: Simple answer, yes. See http://php.net/manual/en/language.types.null.php The special NULL value represents a variable with no value. NULL is the only possible value of type null. You can easily test by performing a var_dump() on the property and you will see both instances it will be NULL class Blah1 { private $foo; function test() { var

问题 And can I therefore safely refactor all instances of class Blah { // ... private $foo = null; // ... } to class Blah { // ... private $foo; // ... } ? 回答1: Simple answer, yes. See http://php.net/manual/en/language.types.null.php The special NULL value represents a variable with no value. NULL is the only possible value of type null. You can easily test by performing a var_dump() on the property and you will see both instances it will be NULL class Blah1 { private $foo; function test() { var

问题 When I provide a constructor with a default value public MyClass(string description = null) { .... } is this equivalent to public MyClass() { .... } public MyClass(string description) { .... } in terms of Serialization . In other words, is a default constructor available ? Practically it is, but will I face some issues when I use serialization? 回答1: No. It unfortunately is not a default constructor. When you write: public MyClass(string description = null) { .... } You're actually making a

问题 Several times (even several in a row) I've been bitten by the defaultdict bug: forgetting that something is actually a defaultdict and treating it like a regular dictionary. d = defaultdict(list) ... try: v = d["key"] except KeyError: print "Sorry, no dice!" For those who have been bitten too, the problem is evident: when d has no key 'key', the v = d["key"] magically creates an empty list and assigns it to both d["key"] and v instead of raising an exception. Which can be quite a pain to

问题 Several times (even several in a row) I've been bitten by the defaultdict bug: forgetting that something is actually a defaultdict and treating it like a regular dictionary. d = defaultdict(list) ... try: v = d["key"] except KeyError: print "Sorry, no dice!" For those who have been bitten too, the problem is evident: when d has no key 'key', the v = d["key"] magically creates an empty list and assigns it to both d["key"] and v instead of raising an exception. Which can be quite a pain to