String manipulation

A string stores text. Use + to concatenate strings; .length gives the number of characters. ERL and Python both start string positions at zero. ERL .substring(start, count) begins at start and takes count characters; Python's slice stops before its end, so use start + count. .left(n) and .right(n) take characters from either end. ERL .upper and .lower change case; Python calls .upper() and .lower().

word = "Revision"
OUTPUT word.length
OUTPUT word.substring(2, 3)
OUTPUT word.left(4)
OUTPUT word.right(4)
OUTPUT word.upper
OUTPUT word.lower

word = "Revision"
print(len(word))
print(word[2:5])
print(word[:4])
print(word[-4:])
print(word.upper())
print(word.lower())

The outputs include 8, vis, Revi and sion.

ASC converts a character to its character-set code; CHR converts a code back to a character. Python uses ord() and chr() for the same jobs. For example, the code for B is 66, and 67 represents the next character, C:

code = ASC("B")
OUTPUT code
OUTPUT CHR(code + 1)

code = ord("B")
print(code)
print(chr(code + 1))

Both versions output 66 and then C.

String operations are often combined. Here, a username is the first three letters of the surname, the first letter of the first name and the year, all in lower case:

first = "Ada"
surname = "Lovelace"
year = 2026
start = surname.left(3)
initial = first.left(1)
username = start.lower + initial.lower + str(year)
print(username)

first = "Ada"
surname = "Lovelace"
year = 2026
start = surname[:3]
initial = first[:1]
username = start.lower() + initial.lower() + str(year)
print(username)

Both print lova2026. str(year) casts the year to a string, because + can't join a string and an integer.

The + operator does different things depending on the data type:

• with two strings, it concatenates them: "15" + "1" gives "151"
• with two numbers, it adds them: 15 + 1 gives 16

Input from the keyboard always arrives as a string. A program that reads two numbers and joins them with + will print 151 instead of 16, unless the inputs are cast with int() first.