python容易被忽略的问题

1、int（）强制转换浮点数

在int（）的强制转换浮点数时候，不管是正数还是负数，只取整数部分。

print(int(6.235))  # 6
print(int(-6.235))  # -6

　　

注意：这里不是向上或者向下取整，也不是四舍五入。

2、注意操作的返回值

a = print("python")
print(a)  # None

list_1 = [1,2,3]
list_2 = [4,5,6]
print(list_1.extend(list_2))  # None
print(list_1)  # [1, 2, 3, 4, 5, 6]

list_3 = [1,6,5,8,7,9,4,1,3]
new_list = list_3.sort()
print(new_list)  # None
print(list_3)  # [1, 1, 3, 4, 5, 6, 7, 8, 9]

list_4 = [1, 6, 5, 8, 7, 9, 4, 1, 3]
new_list = sorted(list_4)
print(new_list)  # # [1, 1, 3, 4, 5, 6, 7, 8, 9]
print(list_4)  # 不变[1, 6, 5, 8, 7, 9, 4, 1, 3]

3、字典中按照键的顺序输出

    dict_1 = {"c": 45254, "a": 333, "b": 908}
    for key in dict_1:
        print(key, dict_1[key])

    for key in sorted(dict_1):
        print(key, dict_1[key])