slicing

The use of basic string manipulation: slicing

2.2.3 Additional Programming Techniques

Additional Programming Techniques — Note 2 of 12

e.g. stringname.subString(startingPosition, numberOfCharacters)

What you need to know

String slicing extracts a portion (substring) of a string based on position indices. Strings are zero-indexed, meaning the first character is at position 0. You can also find the length of a string, convert it to uppercase or lowercase, and extract characters from the left or right.

What to know

Strings are 0-indexed: the first character is at position 0, the second at position 1, etc.
.length gives the number of characters in a string. E.g. "Monday".length = 6.
.substring(start, count) extracts 'count' characters starting from 'start' position.
.left(n) returns the first n characters; .right(n) returns the last n characters.
.upper converts a string to UPPERCASE. E.g. "abcd1234".upper = "ABCD1234".
.lower converts a string to lowercase.
ASC() returns the ASCII code of a character; CHR() returns the character for a given code.
Concatenation joins strings together using +, e.g. pilotCode = a + b + str(c).
OCR to Python: .length → len(text); .left(n) → text[:n]; .right(n) → text[-n:]; .substring(start, count) → text[start:start + count]; .upper / .lower → .upper() / .lower(); ASC() / CHR() → ord() / chr().
In a Python slice text[x:y] the character at position y is NOT included: "Python"[0:3] gives "Pyt" (positions 0, 1 and 2).

Key terms

String Manipulation: The process of performing operations on strings, such as concatenation, slicing, measuring length or changing case.

Exam technique

Mistake:Using a comma instead of + for concatenation. Commas in print() separate items, they DON'T join strings. Use + to concatenate.
Tip:Username/ID generators are common. staffID = surname + str(year), then while staffID.length < 10: staffID = staffID + "x" pads it to length 10.
Tip:str() converts a number to a string for concatenation: str(900) gives "900".

Example:message = "abcd1234" → message.left(4) = "abcd", message.right(4) = "1234", int(message.right(4)) * 2 = 2468.

Code examples

String manipulation in Python

python

word = "ComputerScience"

print(len(word))       # 15 (length)
print(word[0:4])       # "Comp" (first 4 chars)
print(word[3:8])       # "puter" (index 3 to 7)
print(word[-3:])       # "nce" (last 3 chars)
print(word.upper())    # "COMPUTERSCIENCE"
print(word.lower())    # "computerscience"
print(ord("A"))        # 65 (ASCII code)
print(chr(97))         # 'a' (character from code)

String handling quick reference

python

text = "Hello"

print(len(text))          # 5         length
print("Python"[0:3])      # Pyt       substring [start:end], end not included
print(text[:3])           # Hel       left 3 characters
print(text[-2:])          # lo        right 2 characters
print("Hi " + "there")    # Hi there  concatenation
print("hello".upper())    # HELLO     uppercase
print("HELLO".lower())    # hello     lowercase
print(ord("A"))           # 65        ASCII code of a character
print(chr(65))            # A         character for an ASCII code

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Practise 2.2.3 questions

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Revise another OCR GCSE topic: Programming Fundamentals

word = "ComputerScience" print(len(word)) # 15 (length) print(word[0:4]) # "Comp" (first 4 chars) print(word[3:8]) # "puter" (index 3 to 7) print(word[-3:]) # "nce" (last 3 chars) print(word.upper()) # "COMPUTERSCIENCE" print(word.lower()) # "computerscience" print(ord("A")) # 65 (ASCII code) print(chr(97)) # 'a' (character from code)

text = "Hello" print(len(text)) # 5 length print("Python"[0:3]) # Pyt substring [start:end], end not included print(text[:3]) # Hel left 3 characters print(text[-2:]) # lo right 2 characters print("Hi " + "there") # Hi there concatenation print("hello".upper()) # HELLO uppercase print("HELLO".lower()) # hello lowercase print(ord("A")) # 65 ASCII code of a character print(chr(65)) # A character for an ASCII code