python循环函数

python中的for循环

1. <span class="com">#for循环格式（类似Java中的foreach）：for 标识符 in 列表名称 :</span>

2. <span class="pun">>>></span><span class="pln"> movies </span><span class="pun">=</span><span class="pln"> </span><span class="pun">[</span><span class="str">"movie1"</span><span class="pun">,</span><span class="str">"movie2"</span><span class="pun">,</span><span class="str">"movie3"</span><span class="pun">]</span>

3. <span class="pun">>>></span><span class="pln"> </span><span class="kwd">for</span><span class="pln"> item </span><span class="kwd">in</span><span class="pln"> movies </span><span class="pun">:</span>

4. <span class="pln"></span><span class="kwd">print</span><span class="pun">(</span><span class="pln">item</span><span class="pun">)</span>

6. <span class="pln"></span>

7. <span class="pln">movie1</span>

8. <span class="pln">movie2</span>

9. <span class="pln">movie3</span>

python中的for循环类似Java中的foreach循环，固定格式见注释

其中：for表示循环开始，要出现在标识符前面；in将要循环的列表与标识符分隔开；:放在列表名后面，表示处理列表代码开始；请注意，列表处理代码必须放在for循环下面并缩进！！！

当for循环开始时，python会将列表中的每一个值分别赋给标识符，这也意味着每次循环标识符的值都不一样；循环会一直迭代，直到处理完列表中的所有数据。

python中的while循环

1. <span class="com">#while循环格式：while 循环条件 ：</span>

2. <span class="pun">>>></span><span class="pln"> </span><span class="kwd">while</span><span class="pln"> count </span><span class="pun"><</span><span class="pln"> len</span><span class="pun">(</span><span class="pln">movies</span><span class="pun">)</span><span class="pln"> </span><span class="pun">:</span>

3. <span class="pln"></span>print(movies[count])

4. <span class="pln"> count </span><span class="pun">=</span><span class="pln"> count </span><span class="pun">+</span><span class="pln"> </span><span class="lit">1</span>

6. <span class="pln"></span>

7. <span class="pln">movie1</span>

8. <span class="pln">movie2</span>

9. <span class="pln">movie3</span>

while循环与for循环相比，多了条件判断的语句，既可以自定义循环结束的条件

python的判断

1. <span class="kwd">if</span><span class="pln"> </span><span class="pun">满足某个条件</span><span class="pln"> </span><span class="pun">:</span>

2. <span class="pln"> </span><span class="pun">执行某些语句</span>

3. <span class="kwd">else</span><span class="pln"> </span><span class="pun">:</span>

4. <span class="pln"> </span><span class="pun">执行某些语句</span>

注意：if语句与else语句最后都要加上:，且if与else后面要执行的代码都要缩进

python的函数

1. <span class="pun">>>></span><span class="pln"> new_movies </span><span class="pun">=</span><span class="pln"> </span><span class="pun">[</span><span class="str">"movie1"</span><span class="pun">,</span><span class="str">"movie2"</span><span class="pun">,</span><span class="str">"movie3"</span><span class="pun">,[</span><span class="str">"movie4_1"</span><span class="pun">,</span><span class="str">"movie4_2"</span><span class="pun">,[</span><span class="str">"movie_4_3_1"</span><span class="pun">,</span><span class="str">"movie_4_3_2"</span><span class="pun">]],</span><span class="str">"movie5"</span><span class="pun">]</span>

2. <span class="pun">>>></span><span class="pln"> </span><span class="kwd">def</span><span class="pln"> listItems</span><span class="pun">(</span><span class="pln">items</span><span class="pun">)</span><span class="pln"> </span><span class="pun">:</span>

3. <span class="pln">        </span><span class="kwd">for</span><span class="pln"> item </span><span class="kwd">in</span><span class="pln"> items </span><span class="pun">:</span>

4. <span class="pln">            </span><span class="kwd">if</span><span class="pln"> isinstance</span><span class="pun">(</span><span class="pln">item</span><span class="pun">,</span><span class="pln">list</span><span class="pun">)</span><span class="pln"> </span><span class="pun">:</span>

5. <span class="pln">                listItems</span><span class="pun">(</span><span class="pln">item</span><span class="pun">)</span>

6.            <span class="kwd">else</span><span class="pln"> </span><span class="pun">:</span>

7. <span class="pln">                </span><span class="kwd">print</span><span class="pun">(</span><span class="pln">item</span><span class="pun">)</span>

9. <span class="pln"></span>

10. <span class="pun">>>></span><span class="pln"> listItems</span><span class="pun">(</span><span class="pln">new_movies</span><span class="pun">)</span>

11. <span class="pln">movie1</span>

12. <span class="pln">movie2</span>

13. <span class="pln">movie3</span>

14. <span class="pln">movie4_1</span>

15. <span class="pln">movie4_2</span>

16. <span class="pln">movie_4_3_1</span>

17. <span class="pln">movie_4_3_2</span>

18. <span class="pln">movie5</span>

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