1.从文件中读取数据
#从文件中读取数据
with open("pi_digits.txt") as file_abnormal: #open()函数：接受的参数是要打开文件的名称，在当前目录查找指定文件 contents = file_abnormal.read() #方法read（）：读取文件的全部内容，到达文件末尾时返回一个空字符 print(contents) print(contents.rstrip()) print(contents) #文件路径 #要让Python打开不与程序文件位于同一目录中的文件，需要提供文件路径 #相对路径行不通就使用绝对路径 file_path = r'C:\WiFi_log.txt' #绝对路径，不能含中文 with open(file_path) as file_abnormal: test = file_abnormal.read() print(test) #逐行读取 #检查其中的每一行 filename = 'pi_digits.txt' with open(filename) as file_object: #使用关键字with时，open（）返回的文件对象只在with代码块内可用 lines = file_object.readlines() ** #将文件各行存储在一个列表中，只能在with码块外使用** #for line in file_object: #print(line) #print(file_object) ** #只是文件属性？** #print(line.rstrip()) for lin in lines: print(lin.rstrip()) print("\n") #使用文件内容 pi_string = " " for line in lines: #读取文本文件时，Python将所有文本解读为字符串 pi_string += line.strip() #strip():删除空格 #pi_string += line.rstrip() ** #rstrip():清除空白行** print(pi_string) print(len(pi_string)) print(pi_string[:52]) print("\n")
2.#写入文件
filenames = 'programming.txt' ** #创建文件名** with open(filenames,'w') as file_object: ** #w:写入模式** file_object.write("I love programming.\n") #文件对象方法write（）将一个字符串写入文件 file_object.write("I love creating new games.\n") with open(filenames,'a') as file_object: #'a':附加模式把文件内容附加到文件末尾，而不是覆盖内容 file_object.write("I love creating apps that can run in browser.")
3.存储数据
import json #json模块能将简单的Python数据结构存储到文件中 def greet_user(): filename = 'username.json' #创建文件 try: with open(filename) as f_log: ** #注意冒号，打开文件** username = json.load(f_log) #把文件内容加载到变量 except FileNotFoundError: username = input("What is your name? ") #之前没写入则执行except with open(filename,'w') as f_log: #写入模式 json.dump(username,f_log) #json.dump进去 print("We'll remember your when you come back, " + username + "!") else: print("Welcome back , " + username +"!") greet_user() #重构 #代码可以正确的运行，但是可以将代码分为一系列函数来完成 def get_stored_username(): filename = 'username.json' try: with open(filename) as f_log: username = json.load(f_log) except FileNotFoundError: return None else: return username def get_new_username(): filename = "username.json" with open(filename,'w') as f_log: username = input("What is your name? ") json.dump(username,f_log) return username def new_greet_user(): username = get_stored_username() if username: print("Welcome back, " + username + '!') else: username = get_new_username() print("We will remember you when you come back, " + username + '!') #new_greet_user() get_new_username() new_greet_user()
4.异常
#处理ZeroDivisionError异常 #print(5/0)
print("\n") #使用异常避免崩溃 print("Give me two numbers, and I'll divide them.") print("Enter 'q' to quit.") while True: first_number = input("\nFirst number: ") if first_number == 'q': break second_number = input("\nSecond number: ") #if second_number == 'q': #break try: answer = int(first_number) / int(second_number) except ZeroDivisionError: print("You don't divide by 0!")
else:
print(answer)
#处理FileNotFoundError异常 #filename = 'init.txt'
try: with open(filename) as log_object: contents = log_object.read() except FileNotFoundError: ** #避免客户或者*看到异常 print("\nSorry,the file "+ filename + "done't exit.") else: words = contents.split() num_words = len(words) print("The file " + filename + " has about " + str(num_words) + " words.") #使用多个文件 def count_words(filename): #定义函数注意加形参 try: with open(filename) as log_object: contents = log_object.read() except FileNotFoundError: ** # 避免客户或者*看到异常 print("\nSorry,the file " + filename + "done't exit.") else: words = contents.split() num_words = len(words) print("The file " + filename + " has about " + str(num_words) + " words.") filename = 'programming.txt' count_words(filename) print("\n")
def count_words(filename): try: with open(filename) as log_object: contents = log_object.read() except FileNotFoundError: # 避免客户或者看到异常* #print("\nSorry,the file " + filename + "done't exit.") pass #失败时一声不吭，让程序继续运行 else: words = contents.split() num_words = len(words) print("The file " + filename + " has about " + str(num_words) + " words.") filename = 'programming.txt' count_words(filename) filename = ['programming.txt','pi_digits.txt','abc.txt'] for file in filename: #遍历列表传递实参 count_words(file)
