f1 = open(r‘E:\Python\Data\data1.txt‘)  #读取data1.txt文件，使用系统默认缓冲区大小, 为了读取快点，使用缓存吧！

f = open(r‘E:\Python\Data\data2.txt‘, ‘w‘)f.write(‘Hello World !‘)f.close()f = open(r‘E:\Python\Data\data2.txt‘, ‘r‘)p1 = f.read(5)  # 先读5个字节p2 = f.read()   # 余下的都读出来
f.close()

f = open(r‘E:\Python\Data\data3.txt‘)cNames = f.readlines()   #把数据从文件一行行读取，返回一个列表print(cNames)f.close()

#结果， readlines()读取的结果中，不去掉换行符[‘GOOGLE Inc\n‘, ‘Nicrosoft Corporation\n‘, ‘Apple Inc.\n‘, ‘Facebook, Inc.‘]

# Filename:revcopy.pyf1 = open(r‘E:\Python\Data\data3.txt‘)   # 读cNames = f1.readlines() for i in range(0, len(cNames)):    cNames[i] = str(i+1) + ‘.‘ + cNames[i]f1.close()f2 = open(r‘E:\Python\Data\data3_out.txt‘, ‘w‘)  # 写f2.writelines(cNames)f2.close()

s = ‘Tencent Technology Company Limited‘f = open(r‘E:\Python\Data\data3.txt‘, ‘a+‘)f.writelines(‘\n‘)f.writelines(s)f.seek(0, 0)            # 把文件指针移到文件首部cNames = f.readlines()print(cNames)f.close()