python文件访问与函数式编程入门

    file1 = open("test.txt")
    file2 = open("output.txt", "w")

    while True:
        line = file1.readline()
        file2.write('"' + line+'"')
        if not line:
            break
    file1.close()
    file2.close()
    
    read()将文本文件所有行读到一个字符串中
    readline()是一行一行的读
    readlines()是将文本文件中所有行读到一个list中，文本文件每一行是list的一个元素

    #文件迭代器
    file2 = open("output.txt", "w")
    for line in open("test.txt"):
        file2.write('"'+line+'"')
    
    #文件上下文管理器
    with open('somefile.txt', 'r') as f:
        data = f.read()

    with open('somefile.txt', 'r') as f:
        for line in f:

    with open('somefile.txt', 'w') as f:
        f.write(text1)
        f.write(text2)
        ...

    with open('somefile.txt', 'w') as f:
        print(line1, file=f)

 将变量从内存中变成可以存储或传输的过程称为序列化，在Python中叫做pickling，在其他语言中也称为serialization、marshaling、flattening等等。反之，则为反序列化，称为unpickling,把变量内存从序列化的对象重新读取到内存中。

# 序列化
import pickle

d = dict(name = '思聪', age = 29, score = 80)
str = pickle.dumps(d) #调用pickle的dumps函数进行序列化处理
print(str)

f = open('dump.txt', 'wb')
pickle.dump(d, f)
f.close()

# 反序列化
import pickle

f = open('dump.txt', 'rb')
d = pickle.load(f)
f.close()
print(d)
print('name is %s' % d['name'])

python使用lambda来创建匿名函数
Lambda函数只包含一个语句， 如下：
    lambda [arg1 [,arg2,...argn]]:expression

sum = lambda arg1, arg2: arg1 + arg2
sum(10, 20)

def sum(arg1, arg2):
    return arg1 + arg2

#filter
l = [100, 20, 24, 50, 110]
new = list(filter(lambda x: x<50, l))
print(new) # [20, 24]