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读取整个文件
with open('pi_digits.txt') as file_object: contents = file_object.read()
print(contents.rstrip())
注：
with的用法：让文件妥善地打开和关闭。
rstrip（）函数：消除空行
使用文件的内容：
with open('test_files/pi_digits.txt') as file_object: lines =
file_object.readlines() pi_string = '' for line in lines: pi_string +=
line.strip() print(pi_string) print(len(pi_string))
注：读取文本文件时，python将所有文本都解读为字符串。如果读取的是数字，需要用int(）将其转化为整数，使用函数float（）将其转化为浮点数。
生日是否包含在圆周率中
with open('pi_million_digits.txt') as file_object: lines =
file_object.readlines() pi_string = '' for line in lines: pi_string +=
line.strip() birthday = input("Enter your bithday:") if birthday in pi_string:
print("your birtday appears.") else: print("your birthday don't appear.")
#print(pi_string[:6] + "...") print(len(pi_string))
文件写入
filename = 'programing.txt' with open(filename,'a') as file_object:
file_object.write("I also love you.\n") file_object.write("I also love
programing.\n")
注：open函数的几种模式：r:读取模式。w:写入模式 a:附件模式，在原有基础上可以添加其他内容。
写入多行注意用\n：换行符号。
使用多个文件，并且失败时一声不吭。
try,
except的用法：如果try代码块中的代码运行没问题，Python跳过except代码块。如果try代码运行错误，python将查找这样的except模块，并运行代码。
try, except，else模块中，try执行失败，运行except, 运行成功，执行else模块。
def count_number(filename): try: with open(filename) as f_obj: contents =
f_obj.read() except FileNotFoundError: pass else: words = contents.split()
number_words = len(words) print("The novel " + filename +" has " +
str(number_words) + ".") filenames =
['alice.txt','sidd.txt','moby_dict.txt','little_women.txt'] for filename in
filenames: count_number(filename)
决定报告哪些错误，由用户需求决定。
存储数据
使用json来存储数据。
import json def stored_username(): filename = 'username.json' try: with
open(filename) as f_obj: username = json.load(f_obj) except FileNotFoundError:
return None else: return username def get_new_name(): username = input("What's
your name?") filename = 'username.json' with open(filename, 'w') as f_obj:
json.dump(username, f_obj) return username def greet_user(): username =
stored_username() if username: print("welcome back," + username + "!") else:
username = get_new_name() print("We will be happy,when you come," + username +
"!") greet_user()
重构
将代码划分为一系列完成具体工作的函数。这样的过程称为重构。
重构让代码更清晰，更易于理解，更容易扩展。