String operations and function

A string is a sequence of at least zero characters enclosed within (delimiter by) an opened and closed single ( '' ) or double ( "" ) quotation marks. These include any character, even space or numbers. Eg: 'swift Python', "Alan Turing", "Michael Jordan - 23"

String operations

These are operations done on strings objects. These operations are string concatenation and string repetition. We use the addition, +, and multiplication, *, operators, respectively, to concatenate (join) and repeat strings.

Example

Concatenation, in this context, is adding one string to another string.

# String concatenation
first_name = 'Daniel'
last_name  = "Doe"
full_name = first_name + " " + last_name

# we added the first name, space and then the last name to
# produce a full name. The " " is an empty string but
# with space between the delimiters
# output => Daniel Doe
# Without space, we'd have, DanielDoe as the output

# String repetition
# Lets say we want to repeat a particular string for n
# number of times, we do, string * n.
# Lets try to repeat "Hello" three time
h = "Hello"
print(h * 3)
# output=> HelloHelloHello

String function

These function will help us format the string. There is a lot of these functions on the Python docs.

Calling the function

A function as we would discuss later is a piece of code that does something - performs certain computation. Do my_string.function() to call a string function on a string object.

########### String functions ###########

name = "John"

# change of a name to lower case
print(name.lower())

# change of a name to upper case
print(name.upper())

# capitalize of a name - the first character becomes upper
# and the rest lower
print(name.capitalize())

# return string as a title format
print(name.title())

# remove (strip) 'h' from the name
print(name.strip('h'))

# find the length or size (number of characters) in name
print(len(name))

# split a string by some char
str_split = "hello world"
str_list = str_split.split(' ')  # ['hello', 'world']
print(str_list)

# join
list_str = ['hello', 'world']
new_str = " ".join(list_str)
print(new_str)  # "hello world"

# join with some character, say $
list_str = ['hello', 'world']
new_str = "$".join(list_str)
print(new_str)  # "hello$world"

# There is a whole lot on the Python home page

Practical

• Write a program to take input from the user, print the input, separated by a short-dash, -, and the length of the string. Eg: input='Doe', output=Doe - 3
• Write a program that reads data from the user and converts the data to lower case, upper case, title and capitalize.

Summary

• String concatenation - add ( join) one string onto another. Eg: name = 'Future' + ' ' + 'Dann'.
• String repetition - repeat a string for n-times. Eg: print("Green tea" * 2).
• Do my_string.function_name() to call a string function.