[Python知识库]python的一些函数或者用法

1.读取txt文件

    import codecs
    result = []
    with codecs.open("文件名.txt", "rb", 'utf-8', errors='ignore') as txtfile:
        for line in txtfile:
            line = line.replace("\r", "")  # 去除\r
            line = line.replace("\n", "")  # 去除\n
            result.append(line)
    text = ["".join(result)]
    print(text)

2.map函数

map就是方便一堆数据都套一个函数的情景
参数为：map(函数,待此函数处理的数据)
map直接出来的结果是一个对象，因此需要list()等转换成我们需要的格式。

l1 = list(map(lambda x: x**2, [2, 3, 4]))
print(l1)

运行结果
匿名函数为平方

def add(x, y):
    return x+y
l2 = list(map(add, [1, 2, 3], [1, 1, 1]))
print(l2)

运行结果

3.zip函数

用于打包

a = [1, 2, 3]
b = [4, 5, 6, 7]
c = ["A", "B", "C"]
print(list(zip(a, b, c)))

结果

a = [1, 2, 3]
b = [4, 5, 6, 7]
c = ["A", "B", "C"]
for i, j, k in zip(a, b, c):
    print(i, j, k)

结果

交换字典键值对

dic = {}
dic["a"] = 1
dic["b"] = 2
dic["c"] = 3
dic2 = dict(zip(dic.values(), dic.keys()))
print(dic)
print(dic2)

结果