我们用一个提取字符串内单词首字母的程序先热热身，比如输入：
程序把缩写OMG输出来。
# ---------- PROBLEM : ACRONYM GENERATOR ----------
# You will enter a string and then convert it to an acronym
# with uppercase letters like this
'''
Convert to Acronym : Random Access Memory
RAM
'''
# Ask for a string
str1 = input("Convert to Acronym : ")
# Convert the string to all uppercase
str1 = str1.upper()
# Covert the string into a list
listOfWords = str1.split()
print(listOfWords)
# Cycle through the list
for word in listOfWords:
# Print the 1st letter of the word
print(word[0], end='')
第二个程序是为了解决小甲鱼的烦恼，事情是这样哒：
小甲鱼好不容易鼓起勇气给仰慕已久的女神发了条表白信息，
最添彩那句就是“我的爱意有如长江之水滔滔不绝，如黄河泛滥一发不可收拾“，
不曾想却被心怀叵测、唯一戏份就是搞破坏滴第三者把这条信息给拦截下来了，不仅进行了可耻滴偷窥还卑鄙滴把”爱“字篡改成了”恨“字。
收到信的美眉很生气
后果很严重！小甲鱼百般解释千般赔罪，女神才答应不把他拉黑，这样的事说啥也不能重演啦！！！
内个，这个桥段是不是看着眼熟，不用回忆啦，某类言情剧或小说里随便一抓哒～～～
痛定思痛的小甲鱼决定委托我们写一个字符串加密程序，这样传输过程中信息就算被偷看被拦截也不知所谓，更谈不上做篡改。
加密方法是每个字符变成自己的unicode或跟unicode有关的数字串密文，密文到达目的地后还得要解密，绝不能惊扰美眉对仰慕者情书“随便一瞄”“淡淡一笑”再优雅滴“随手一放”的姿态。
# ---------- PROBLEM : SECRET STRING ----------
# Input string to be encrypted and initiate values
orig_message = input("Enter a string: ")
# initiate value for encrypted string
secret_message = ''
# cycle through each character in the string
for char in orig_message:
tempCode = str(ord(char) - 27)
if len(tempCode) == 1:
tempCode = '0' + tempCode
# store each character code in secret message
secret_message += tempCode
# Print encrypted message
print("Secret message: ", secret_message)
# Cycle through two character code at a time
norm_string = ""
for i in range(0, len(secret_message)-1, 2):
# Convert the code into characters and add them to the string
char_code = int(secret_message[i] + secret_message[i+1])
norm_string += chr(char_code + 27)
# Print the string
print("Original message : ", norm_string)
凯撒加密是一种简单且广为人知的加密技术。它把明文中的所有字母都在字母表上向后（或向前）按照一个固定数目进行偏移，而后被替换成密文。
传说在战场上凯撒用这种密文来跟他的将军们进行通信，“Attack at Dawn!"的密文根据偏移量不同而不同，偏移量为3时，加密结果是“Dwwdfn dw Gdzq”。
这样，就算密信被混入军团里的奸细窃取到，不知道偏移量他跟看天书没区别。
但那是当时，现在这样可不中。
现在都是把凯撒加密和其他更复杂的加密方法结合起来使用，不然一会儿就会被破解哒，虽然我们就是写了一个凯撒加密解密字符串的程序。
# ---------- PROBLEM : CAESAR'S CIPHER ----------
# Receive a message and then encrypt it by shifting the
# characters by a requested amount to the right
# A becomes D, B becomes E for example
# Also decrypt the message back again
# Receive the message to encrypt and the number of characters to shift
message = input("Enter your message: ")
key = int(input("How many characters should we shift(-26 ~ 26) "))
# Prepare your secret message
secret_message = ''
# Cycle through each character in the message
for char in message:
# if it is a letter
if char.isalpha():
# Get unicode and add the shift amount
char_code = ord(char) + key
# if uppercase
if char.isupper():
# if greater than 'Z'
if char_code > ord('Z'):
char_code -= 26
# if less than 'A'
if char_code < ord('A'):
char_code += 26
# if lowercase
if char.islower():
# if greater than 'z'
if char_code > ord('z'):
char_code -= 26
# if less than 'a'
if char_code < ord('a'):
char_code += 26
# Convert from code to letter and add to message
secret_message += chr(char_code)
# if not a letter leave the character as is
else:
secret_message += char
# print the encrypted message
print("Encrypted message: ", secret_message)
# To decrypt the only thing that changes is the sign of the key
key = -key
orig_message = ""
for char in secret_message:
# if it is a letter
if char.isalpha():
# Get unicode and add the shift amount
char_code = ord(char) + key
# if uppercase
if char.isupper():
# if greater than 'Z'
if char_code > ord('Z'):
char_code -= 26
# if less than 'A'
if char_code < ord('A'):
char_code += 26
# if lowercase
if char.islower():
# if greater than 'z'
if char_code > ord('z'):
char_code -= 26
# if less than 'a'
if char_code < ord('a'):
char_code += 26
# Convert from code to letter and add to message
orig_message += chr(char_code)
# if not a letter leave the character as is
else:
orig_message += char
print("Decrypted message: ", orig_message)
详情请见视频：