Modifying Text¶
We can loop through the string and modify it using find and slice (substring).
Google has been digitizing books. But, sometimes the digitizer makes a mistake and uses 1 for i. The following program replaces 1 with i everywhere in the string. Now you might not want to really replace every 1 with i, but don’t worry about that right now. It uses a while loop since we don’t know how many times it will need to loop.
Activity: CodeLens 1 (Change_Ones)
You don’t have to replace just one character. You could replace every instance of a word with another word. For example, what if you spelled a word wrong and wanted to change it everywhere?
Activity: CodeLens 2 (Change_Word)
Can you loop through and encode a string to hide the contents of the message?
Activity: CodeLens 3 (Encode_String)
- a
- The letter in str is replaced with the letter at the same position in eStr.
- d
- The letter in str is replaced with the letter at the same position in eStr.
- w
- Try counting the letters in str to figure out how many letters to count in eStr.
- v
- The letter e is at position 4 in str and will be replaced with the letter v at position 4 in eStr.
csp-9-4-4: What character is e replaced with when the message is encoded?
- ""
- It starts out as the empty string, but a letter is added each time through the loop.
- "o"
- The letter in str is replaced with the letter at the same position in eStr.
- "n"
- The letter in eStr at the same position as the m in str is n.
- "m"
- Notice that we are adding the letter in eStr at pos not the letter in str at pos.
csp-9-4-5: What is the value of encodedMessage after the loop executes the first time?
csp-9-4-6 The program below decodes an encoded message, but the lines are mixed up. Put the lines in the right order with the right indentation.message = ""
str = "abcdefghijklmnopqrstuvwxyz. "
eStr = "zyxwvutsrqponmlkjihgfedcba ."
encodedMessage = "nvvg.nv.zg.nrwmrtsg"
---
for letter in encodedMessage:
---
pos = eStr.find(letter)
---
message = message + str[pos:pos+1]
---
print(message)