50 — Strings: slicing and changing text

A string is a row of characters counted from 0; slicing cuts a piece out, and a few methods change the text — all ordinary Python, passed through unchanged.

#Steps

1. text[start:end] cuts from start up to but not including end; negative indexes count from the end, so text[-3:] is the last three. It prints hello, NME, then NME and NME:

   text = "hello NME"
   show text[0:5]
   show text[6:9]
   show text[-3:]
   show text[-4:]
   

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2. .upper() and .lower() change case into a new string; .replace("a", "o") swaps every occurrence, find first and replacement second. They print HELLO NME, hello nme, and bononos:

   text = "hello NME"
   show text.upper()
   show text.lower()
   

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   text = "bananas"
   show text.replace("a", "o")
   

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3. .strip() removes spaces from both ends, which cleans up typed input; it prints hello:

   text = "  hello  "
   show text.strip()
   

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4. All together, saved as strings.nme. A real typed line keeps edge spaces, so the program strips it, slices pieces, and splits the clean text into words:

   # strings.nme — slice and change a sentence.
   # Run: nme r strings
   # Python string tools: slicing, case, replace, and strip.
   
   ask text, "Type a sentence: "
   
   show f"Original: {text}"
   show f"Length: {len(text)} characters"
   show f"First five characters: {text[0:5]}"
   show f"Last three characters: {text[-3:]}"
   show f"Slice from index 2 to 10: {text[2:10]}"
   show f"Uppercase: {text.upper()}"
   show f"Lowercase: {text.lower()}"
   show f"Without edge spaces: {text.strip()}"
   show f"Swap a for o: {text.replace('a', 'o')}"
   
   clean = text.strip()
   words = clean.split()
   show f"Trimmed to {len(clean)} characters: {clean}"
   show f"First character of the trimmed text: {clean[0]}"
   show f"Last character of the trimmed text: {clean[-1]}"
   show f"{len(words)} words; the first is {words[0]} and the last is {words[-1]}"
   show "Each word, one per line:"
   for word in words:
       show word
   

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5. Run it with a sentence piped in — the typed line keeps its edge spaces:

   printf '  I love bananas  \n' | nme r strings
   

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   Type a sentence: Original:   I love bananas  
   Length: 18 characters
   First five characters:   I l
   Last three characters: s  
   Slice from index 2 to 10: I love b
   Uppercase:   I LOVE BANANAS  
   Lowercase:   i love bananas  
   Without edge spaces: I love bananas
   Swap a for o:   I love bononos  
   Trimmed to 14 characters: I love bananas
   First character of the trimmed text: I
   Last character of the trimmed text: s
   3 words; the first is I and the last is bananas
   Each word, one per line:
   I
   love
   bananas
   

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   bananas becomes bononos when every a is swapped for o; the other spaces stay because the slices and .replace() use the untrimmed original.

#Try it yourself

Ask for a second sentence, strip it, and print its first word. Swap two letters and count the characters with len before and after strip.

#What you learned

• text[start:end] cuts a slice; text[-3:] starts from the end.
• .upper() / .lower() change case and make a new string.
• .replace("a", "o") swaps every occurrence of one text for another.
• .strip() removes spaces at both ends of a string.