String manipulation

Strings are a collection of stored under one identifier. They can be thought of as an array of characters. There are a variety of different ways we can manipulate strings.

As a string behaves like an array of characters, we can access individual characters in a string. Strings are referenced by , starting at 0.

name = 'walter'
name[0] = w
name[1] = a
name[2] = l
name[3] = t
name[4] = e
name[5] = r

Concatenation

Strings can be joined together to form a new string of data. This is called concatenation. We use the + symbol to concatenate strings. For example:

fname = 'walter'
sname = 'white'
name = fname + ' ' + sname

This will produce the output: walter white. Note the space (' ').

Character searching

We can determine if an individual character is found in a string using the 'in' keyword. This will return True/False:

'f' in sname = False
'e' in fname = True

This also works with substrings (subset of characters):

'alt' in fname = True

String splitting

It is possible to find part of a string by using a subString (a bit, or part, of a string) method. Remember that the first character in the string starts at reference 0.

For example, select a substring from character 2 to character 4 (remember, the slice will stop before element 4):

fname.subString(2,4) = lt

In Python, this can be implemented as:

fname[2:4] = lt

Python provides the ability to slice strings. Slicing characters from a string allows programmers to select any characters that they want from a string.

You can set the element you want to start the slice at, which element you want to finish at, and the increments or decrements you want. For example:

fname[0:5:2] = wle

This returns a character, then moves forward 2 positions and returns the next character until character 5.

Common string manipulation techniques

Command	Description	Example	Output
.length	This returns the number of characters in the string. This will include spaces	fname.length	6
.upper	This changes all the characters in the string to upper case	name.upper	WALTER
.lower	This changes all the characters in the string to lower case	name.lower	walter
[n]	This selects a particular character in the string	fname[2]	l
.subString(x,y)	This selects a particular part of a string. It starts at the place in the string set by x and selects the next character, set by y	fname.subString(1,2)	al
str()	This converts any data into the string data type	str(fname)	-
ASC	This will return the ascii number of the character	ASC(fname[0])	A - 119
Chr	This will return the ascii character of a number	CHR(65)	A

Command	.length
Description	This returns the number of characters in the string. This will include spaces
Example	fname.length
Output	6

Command	.upper
Description	This changes all the characters in the string to upper case
Example	name.upper
Output	WALTER

Command	.lower
Description	This changes all the characters in the string to lower case
Example	name.lower
Output	walter

Command	[n]
Description	This selects a particular character in the string
Example	fname[2]
Output	l

Command	.subString(x,y)
Description	This selects a particular part of a string. It starts at the place in the string set by x and selects the next character, set by y
Example	fname.subString(1,2)
Output	al

Command	str()
Description	This converts any data into the string data type
Example	str(fname)
Output	-

Command	ASC
Description	This will return the ascii number of the character
Example	ASC(fname[0])
Output	A - 119

Command	Chr
Description	This will return the ascii character of a number
Example	CHR(65)
Output	A

Programming constructs - CCEAString manipulation