such as和for example前面加不加逗号

1.such as和for example前面可以加逗号.
2.it has a population of around 23000000可以换成it has a population,around 23000000.around 前可以加逗号.
3.区别：
such as + 词组或单词,“如象”
for example=for instance ,“例如”,后根句子,如果要举例,