Python编程：从入门到实践（课后习题10）

# 10-6 加法运算
first_number = input("First number: ")
second_number = input("Second number: ")
try:
add = int(first_number) + int(second_number)
except ValueError:
print("You must enter digits!!!")
else:
print(add)

# 10-7 加法计算器
print("Please enter two digits, I will add the two numbers.")
print("Enter 'q' to quit.")

while True:
first_number = input("First number: ")
if first_number == 'q':
break
second_number = input("Second number: ")

try:
add = int(first_number) + int(second_number)
except ValueError:
print("You must enter digits!!!\n")
else:
print(add)

# 10-8 猫和狗
filename_cat = 'd:/cats.txt'
filename_dog = 'd:/dogs.txt'
with open(filename_cat) as cat:
cats = cat.read()
print(cats)
with open(filename_dog) as dog:
dogs = dog.read()
print(dogs)
cats.close()
dogs.close()

try:
with open(filename_cat) as cat:
cats = cat.read()
except FileNotFoundError:
print(filename_cat + " has no exsit.")
else:
print(cats)

# 10-9 沉默的猫和狗
try:
with open(filename_cat) as cat:
cats = cat.read()
except FileNotFoundError:
pass
else:
print(cats)

#10-10 常见单词
filename = 'd:/gutenberg.txt'
try:
with open(filename) as gutenberg:
gu_read = gutenberg.read()
splitx = gu_read.split()
except FileNotFoundError:
print(filename_cat + " has no exsit.")
else:
counts = splitx.count('the')
print(counts)

# 10-11 喜欢的数字
import json
filename = 'numbers.json'
numbers = input("Enter a number you like: ")
with open(filename, 'w') as f_obj:
json.dump(numbers, f_obj)

with open(filename) as f_obj:
numbers = json.load(f_obj)
print("I know your favorite number! It's " + str(numbers) + ".")

# 10-12 记住喜欢的数字
import json
filename = 'numbers.json'
try:
with open(filename) as f_obj:
numbers = json.load(f_obj)
except FileNotFoundError:
numbers = input("Enter a number you like: ")
with open(filename, 'w') as f_obj:
json.dump(numbers, f_obj)
print("I remember this number you like.")
else:
print("I know your favorite number! It's " + str(numbers) + ".")

#10-13验证用户
import json

def get_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_username():
username = input("What is your name? ")
filename = 'username.json'
with open(filename, 'w') as f_obj:
json.dump(username, f_obj)
return username

def greet_user():
username = get_stored_username()
if username:
print("Is your name this: " + username + "?")
yn = input("Enter 'y' is yes, 'n' is no. ")
if yn == 'y':
print("Welcome back " + username + "!")
else:
username = get_new_username()
print("We'll remember you when you come back, " + username + "!")
else:
username = get_new_username()
print("We'll remember you when you come back, " + username + "!")

greet_user()