if(condition_if){

    commands_if;

} else { // 可选

    commands_else;

}

if(condition_if1){

    commands_if1;

} else if (condition_if2) {

    commands_if2;

} else{ //可选

commands_else;

}

switch (condition){

  case case1:

    comands_1;

    break; // 可选

  case case2:

    comands_2;

    break; // 可选

  default:

    commands_default;

}

if condition_if：

    commands_if

else: # 可选

    commands_else

if condition_1:

    commands_1;

elif condition_2:

    commands_2

else: # 可选

    commands_else