assignment-operator

问题 I have face this weird behavior I can not find explications about. MWE: l = [1] l += {'a': 2} l [1, 'a'] l + {'B': 3} Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: can only concatenate list (not "dict") to list Basically, when I += python does not raise an error and append the key to the list while when I only compute the + I get the expected TypeError . Note: this is Python 3.6.10 回答1: l += ... is actually calling object.__iadd__(self, other) and modifies

问题 I have face this weird behavior I can not find explications about. MWE: l = [1] l += {'a': 2} l [1, 'a'] l + {'B': 3} Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: can only concatenate list (not "dict") to list Basically, when I += python does not raise an error and append the key to the list while when I only compute the + I get the expected TypeError . Note: this is Python 3.6.10 回答1: l += ... is actually calling object.__iadd__(self, other) and modifies

问题 I have face this weird behavior I can not find explications about. MWE: l = [1] l += {'a': 2} l [1, 'a'] l + {'B': 3} Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: can only concatenate list (not "dict") to list Basically, when I += python does not raise an error and append the key to the list while when I only compute the + I get the expected TypeError . Note: this is Python 3.6.10 回答1: l += ... is actually calling object.__iadd__(self, other) and modifies

问题 I have face this weird behavior I can not find explications about. MWE: l = [1] l += {'a': 2} l [1, 'a'] l + {'B': 3} Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: can only concatenate list (not "dict") to list Basically, when I += python does not raise an error and append the key to the list while when I only compute the + I get the expected TypeError . Note: this is Python 3.6.10 回答1: l += ... is actually calling object.__iadd__(self, other) and modifies

问题 I have face this weird behavior I can not find explications about. MWE: l = [1] l += {'a': 2} l [1, 'a'] l + {'B': 3} Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: can only concatenate list (not "dict") to list Basically, when I += python does not raise an error and append the key to the list while when I only compute the + I get the expected TypeError . Note: this is Python 3.6.10 回答1: l += ... is actually calling object.__iadd__(self, other) and modifies

问题 if ((vnd = (struct diam_vnd_t *)g_hash_table_lookup(vendors,vend))) {...} Can you tell me why it is an assignment but not a boolean expression in the brackets ? And in what situation this assignment can be considered "true" or "false" ? 回答1: Quoting C11 , chapter §6.5.16, Assignment operators ( emphasis mine ) An assignment operator stores a value in the object designated by the left operand. An assignment expression has the value of the left operand after the assignment, 111) but is not an

问题 if ((vnd = (struct diam_vnd_t *)g_hash_table_lookup(vendors,vend))) {...} Can you tell me why it is an assignment but not a boolean expression in the brackets ? And in what situation this assignment can be considered "true" or "false" ? 回答1: Quoting C11 , chapter §6.5.16, Assignment operators ( emphasis mine ) An assignment operator stores a value in the object designated by the left operand. An assignment expression has the value of the left operand after the assignment, 111) but is not an

问题 I am learning c. I have a question. Why doesn't my program work? #include<stdio.h> #include<conio.h> #include<stdlib.h> char cmd; void exec() { if (cmd == "e") { printf("%c", cmd); // exit(0); } else { printf("Illegal Arg"); } } void input() { scanf("%c", &cmd); exec(); } int main() { input(); return 0; } I insert a "e" but it says illegal arg. cmd is not equal to "e". Why? I set cmd with scanf to "e". 回答1: First of, in C single quotes are char literals, and double quotes are string literals.

来源： https://stackoverflow.com/questions/39548639/assign-one-class-object-to-another-class-object-in-c

来源： https://stackoverflow.com/questions/39548639/assign-one-class-object-to-another-class-object-in-c