GCSEComputer ScienceEdexcelRevision Notes6. Problem Solving with ProgrammingData Types & Data StructuresProgramming String Manipulation

Programming String Manipulation (Edexcel GCSE Computer Science)

Revision Note

James Woodhouse

Programming 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:

    • Length (analyse)

    • Position (analyse)

    • Substrings (extract)

    • Case conversion (modify)

    • Concatenation (modify)

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

Python

Output

Length

Password = "letmein"

print(len(Password))

7

Password = "letmein"

if len(Password) >= 8:

print("Password accepted")

else:

print("Password too short")

"Password too short"

Position

  • Position refers to the index or location of a character in a string

  • positions in strings, just like arrays, are 0 indexed (the first value is 0, not 1)

  • A position of a certain word of character from a string can be found using the following:

    • words = "Hello, World!"
      Find the position of the letter e
      print(words.index('e'))

    • The output would be 1

Substring

  • Substring and slicing perform similar tasks in programming

  • Substring is the ability to extract a sequence of characters from a larger string 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 a specific start and end to slice out the desired characters

  • Substring is 0 indexed

Function

Python

Output

 Substring


string[start character : end character]

 

Word = "Revision"

print(Word[2:5])

"vis"

left(number of characters)

 

Word = "Revision"

print(Word[:4])

"Revi"

right(number of characters)

 

Word = "Revision"

print(Word[4:])

"sion"

Case conversion

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

Function

Python

Output

Uppercase

Name = "Sarah"

print(Name.upper())

"SARAH"

Lowercase

Name = "SARAH"

print(Name.lower())

"sarah"

Title case

Book = "inspector calls"

print(Book.title())

"Inspector Calls"

Concatenation

  • The ability to join two or more strings together to form a single string

  • Concatenation uses the '+' operator to join strings together

Function

Python

Output

Concatenation

FName = "Sarah"

SName = "Jones"

FullName = FName + SName

print(FullName)

"SarahJones"

FName = "Sarah"

SName = "Jones"

FullName = FName + " " + SName

print(FullName)

"Sarah Jones"

Name = "Sarah"

print("Hello, " + Name)

"Hello, Sarah"

Examiner 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)

  • FName.substring(0,1) 1 mark

  • LName.substring(0,3) 1 mark

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

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    James Woodhouse

    Author: James Woodhouse

    Expertise: Computer Science

    James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.

    Lucy Kirkham

    Author: Lucy Kirkham

    Expertise: Head of STEM

    Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.