String Manipulation

What is string manipulation?

String manipulation is the use of programming techniques to modify, analyse or extract information from a string
Examples of string manipulation include:
- Case conversion (modify)
- Length (analyse)
- Substrings (extract)
- Concatenation (modify)
- ASCII conversion (analyse)

Case conversion

The ability to change a string from one case to another, for example, lower case to upper case

Function	OCR exam reference	Python	Output
Uppercase	`Name = "Sarah"` `print(Name.upper)`	`Name = "Sarah"` `print(Name.upper())`	"SARAH"
Lowercase	`Name = "SARAH"` `print(Name.lower)`	`Name = "SARAH"` `print(Name.lower())`	"sarah"
Title case	`Book = "inspector calls"` `print(Book.title)`	`Book = "inspector calls"` `print(Book.title())`	"Inspector Calls"

Length

The ability to count the number of characters in a string, for example, checking a password meets the minimum requirement of 8 characters

Function OCR exam reference Python Output

Length

Password = "letmein"

print(Password.length)

Password = "letmein"

print(len(Password))

Password = "letmein"

if Password.length >= 8 then

print("Password accepted")

else

print("Password too short")

end if

Password = "letmein"

if len(Password) >= 8:

print("Password accepted")

else:

print("Password too short")

"Password too short"

Substring

The ability to extract a sequence of characters from a larger string in order to be used by another function in the program, for example, data validation or combining it with other strings
Extracting substrings is performed using 'slicing', using specific start and end to slice out the desired characters
Substring is 0 indexed (first value is 0 not 1)

Function	OCR exam reference	Python	Output
Substring	.substring(starting character, number of characters)	string[start character : end character]
	`Word = "Revision"` `print(Word.substring(2,3))`	`Word = "Revision"` `print(Word[2:5])`	"vis"
	.left(number of characters)
	`Word = "Revision"` `print(Word.left(4))`	`Word = "Revision"` `print(Word[:4])`	"Revi"
	.right(number of characters)
	`Word = "Revision"` `print(Word.right(4))`	`Word = "Revision"` `print(Word[4:])`	"sion"

Concatenation

The ability to join two or more strings together to form a single string
Concatenation uses the '+' operator to join strings together

Function	OCR exam reference	Python	Output
Concatenation	`FName = "Sarah"` `SName = "Jones"` `FullName = FName + SName` `print(FullName)`	`FName = "Sarah"` `SName = "Jones"` `FullName = FName + SName` `print(FullName)`	"SarahJones"
	`FName = "Sarah"` `SName = "Jones"` `FullName = FName + " " + SName` `print(FullName)`	`FName = "Sarah"` `SName = "Jones"` `FullName = FName + " " + SName` `print(FullName)`	"Sarah Jones"
	`Name = "Sarah"` `print("Hello, " + Name)`	`Name = "Sarah"` `print("Hello, " + Name)`	"Hello, Sarah"

ASCII conversion

The ability to return an ASCII character from a numerical value and vice versa

Function	OCR exam reference	Python	Output
ASCII conversion	`print(ASC(A))`	`print(ord("A"))`	"65"
ASCII conversion	`print(CHR(97))`	`print(chr(97))`	"a"

Exam Tip

Remember that the '+' operator is used for concatenation of strings BUT is also the mathematical operator for addition

It is important to remember, that the same operator symbol performs different roles on different types of data (integer/string)

Worked example

A school wants to use a program to take a students first name, last name and year of entry as inputs and use them to create a username

They want the username to follow the rule:

Initial + First 3 letters of last name + year

For example, a student named David Hamilton who started in 2024 would have the username:

DHam2024

The algorithm has been started below:

Line	Algorithm
01	`FName = input("Enter first name")`
02	`LName = input("Enter last name")`
03	`year = input("Enter year")`
04	`username =`
05	`print(username)`

Use string manipulation to complete line 04 to create the username [3]

How to answer this question

What techniques do we need to use to create the username? substring to extract the parts of the first and last name
Concatenation to join them together

Answer

Line	Algorithm
01	`FName = input("Enter first name")`
02	`LName = input("Enter last name")`
03	`year = input("Enter year")`
04	`username = FName.substring(0,1) + LName.substring(0,3) + year`
05	`print(username)`

Guidance

FName.substring(0,1) 1 mark
LName.substring(0,3) 1 mark
username = FName.substring(0,1) + LName.substring(0,3) + year 1 mark

String Manipulation (OCR GCSE Computer Science)

Revision Note