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第十章文件和异常
#1. #A:使用关键字with后,会在不需要访问文件后将其关闭 #B:open(),默认以"r"的形式打开文件,close()分别用于关闭文件 #C:读取文件的方法:read()默认读取整个文件,可以指定读取字节。readline()读取一行,readlines()按行读取后存入列表,当传入读取字节数目后,则读取的内容可能是行的一部分 #D:python3将文件当做一个可迭代的类型,此方法比较好 #E:seek()设置开始读的位置, tell()得到当前开始读取位置 #Test.txt内容是12\r\n22\r\n32 with open("Test.txt") as pFile: buffFile = pFile.read() #buffFile = ‘12\n22\n32‘ with open("Test.txt", "rb") as pFile: buffFile = pFile.read() #buffFile = b‘12\r\n22\r\n32‘ with open("Test.txt", "rb") as pFile: buffFile = pFile.read(4) #buffFile = b‘12\r\n pFile = open("Test.txt") buffFile = pFile.readline() #buffFile = ‘12\n‘ pFile.close() buffFile = "" with open("Test.txt") as pFile: buffFile = pFile.readlines()#buffFile = [‘12\n‘, ‘22\n‘, ‘32\n‘] pFile = open("Test.txt") buffFile = ‘‘ for line in pFile: #python3将文件当做一个可迭代的类型 buffFile += line #buffFile = ‘12\n22\n32‘ pFile.close() pFile = open("Test.txt") pFile.seek(1) value = http://www.mamicode.com/pFile.tell() #value = 1"Test.dat") as pFile: buffFile = pFile.read() #buffFile = ‘1\n2\n3\n4‘ with open("Test.dat", "rb") as pFile: buffFile = pFile.read() #buffFile = b‘1\r2\r\n3\n4‘ with open("Test.dat", "r", newline = "") as pFile: buffFile = pFile.read() #buffFile = ‘1\r2\r\n3\n4‘ #TestWithNull.dat内容:‘1‘, 0x0d, ‘2‘, 0x0d, 0x0a, ‘3‘, 0x0a, ‘4‘, 0, 0 with open("TestWithNull.dat", "rb") as pFile: buffFile = pFile.read() #buffFile = b‘1\r2\r\n3\n4\x00\x00‘ #3. #A:write()用于写入文件 #B:writelines()用于写入多行 with open("Write.txt", "wb") as pFile: pFile.write(b‘1\r2\r\n3\n4\x00\x00‘) #文件中内容:0x31 0x0d 0x32 0x0d 0x0a 0x33 0x0a 0x34 0x00 0x00 with open("Write.txt", "w") as pFile: pFile.write(‘1\r2\r\n3\n4\x00\x00‘) #文件内容:0x31 0x0d 0x32 0x0d 0x0d 0x0a 0x33 0x0d 0x0a 0x34 0x00 0x00 with open("Write.txt", "w", newline = ‘‘) as pFile: pFile.write(‘1\r2\r\n3\n4\x00\x00‘) #文件内容:0x31 0x0d 0x32 0x0d 0x0a 0x33 0x0a 0x34 0x00 0x00 with open("Write.txt", "w") as pFile: # pFile.write(b‘1\r2\r\n3\n4\x00\x00‘) #运行时候报错:must be str, not bytes pass value = http://www.mamicode.com/["123", ‘456‘] with open("Write.txt", "w") as pFile: # pFile.write(value) #运行时候报错:must be str, not list pass value = http://www.mamicode.com/["123", ‘456‘] with open("Write.txt", "w") as pFile: pFile.writelines(value) #文件内容:123456 #4. #A:python使用异常来管理程序执行期间发生的错误。每当发送错误的时候,都会创建一个异常对象,若编写了处理该异常的代码,则程序会继续运行,否则会报错 #B:split()根据字符串创建一个单词列表 #C:pass语句充当占位符,表示当前不做任何事 #value = http://www.mamicode.com/1 / 0 #此处会出现异常"Error") #Error else: print(‘Not Error‘) try: value = http://www.mamicode.com/1 / 1"Error") else: print(‘Not Error‘) #Not error try: pFile = open("NotExitFile.dat") except FileNotFoundError: print(‘File Not Find‘) #File Not Find else: pFile.close() value = http://www.mamicode.com/‘hello world bad world‘"people" : [{"A" : 90}, {"B" : 80}, {"C" : 70}],"data" : 10}‘ jsonValue = http://www.mamicode.com/json.loads(value) #jsonValue = {"people" : [{"A" : 90}, {"B" : 80}, {"C" : 70}],"data" : 10} data = http://www.mamicode.com/jsonValue[‘people‘] #data = [{‘A‘: 90}, {‘B‘: 80}, {‘C‘: 70}]"people" : [{"A" : 90}, {"B" : 80}, {"C" : 70}],"data" : 10, "Test": "szn"} value = http://www.mamicode.com/{"people" : [{"A" : 90}, {"B" : 80}, {"C" : 70}],"data" : 10}; json_str = json.dumps(value) #json_str = ‘{"data": 10, "people": [{"A": 90}, {"B": 80}, {"C": 70}]}‘ with open("JsonFile.json", "w") as pFile: json.dump(value, pFile) #文件内容:{"data": 10, "people": [{"A": 90}, {"B": 80}, {"C": 70}]} with open("JsonFile.json") as pFile: buff = json.load(pFile) #buff = ‘{"data": 10, "people": [{"A": 90}, {"B": 80}, {"C": 70}]}‘ value = http://www.mamicode.com/{1:2, ‘1‘:2} #value = {1: 2, ‘1‘: 2}"1": 2, "1": 2}‘ Test = json.loads(json_str) #Test = {‘1‘: 2}
第十章文件和异常
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