Python : String Manipulations

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String Manipulations

Let's now see in a little more detail how to create and manipulate character strings (Strings) with Python.

A variable of type String can be created with single or double quotes

name = 'Mike'

# or

name = "Mike"

Python allows you to insert special characters into your Strings.

message = "Hello \nWorld"
print(message)
# Hello
# World

The special character “\n” will be replaced by a line break. Python provides you with several special characters. Here is a list: https://www.w3schools.com/python/gloss_python_escape_characters.asp

Interpolation

Using the “f” prefix displays the contents of the variable specified between the brackets {}

name = "Mike"

print(f"Hello {name}")
# Hello Mike

Python can also execute any expression inside the {} brackets, so this concept can become very powerful. Here is an example:

name = "Mike"

print(f"Hello {name.upper()}")
# Hello MIKE

It is also possible to join two Strings with the "+" (plus) operator

name = "Mike"

print("Hello " + name)
# Hello Mike

Ignore special characters

Using the “r” prefix displays the contents of the String as is. That is to say without taking into account special characters (ex. \n)

message = r"https:\\example.com\index.html"
print(message)
# https:\\example.com\index.html

Here the use of the “r” prefix allows the path to be displayed correctly. Otherwise Python would have interpreted the double backslash "\\" as a special character.

String over multiple lines

Python also allows you to create a String exactly as entered even with line breaks. To do this you must use three quotes.

message = """This is multiline
String that is easier to
read and assign"""

print(message)
# This is multiline
# String that is easier to
# read and assign

As a result, reading the String in the code is very explicit.

Retrieving part of String

Python allows to retrieve only part of the String.

A String variable is indeed composed of several characters that can be read one by one or in groups. Here is some example

product = "iPhone 12"
# position 012345678

print(product[0]) 
# i

print(product[2]) 
# h

print(product[1:6])
# Phone

Each character is associated with a position number. The first position is always 0. To access a particular position, it must be specified between square brackets []

Note that it is not possible to modify the String in this way. Any attempt to modify will return an error.

product = "iPhone 12"
product[0] = "e"

# TypeError: 'str' object does not support item assignment

It is possible to access the characters of the String from the end.

message = "Hello World";

print(message[-1])
# d

Position -1 represents the last character, -2 the penultimate, and so on.

When retrieving several characters, if one of the two positions is omitted, the retrieval will be from the beginning of the String

message = "Hello World";

print(message[:5])
# Hello

print(message[-5:])
# World

String Manipulations

Python has several functions that allow you to transform the contents of the String. Here are a few :

Uppercase and lowercase conversion

name = 'Mike Taylor'

print(name.lower())
# mike taylor

print(name.upper())
# MIKE TAYLOR

Remove white spaces before and after a String

message = "  Hello World        "

print(message.strip())
# "Hello World"

Return the number of characters in the String

name = "Mike Taylor"

nb_char = len(name)

print(nb_char)
# 11

Change the first letter of a String to uppercase

name = "mike"

name_cap = name.capitalize() 

print(name_cap)
# Mike

Change the first letter of all words in a String to uppercase

name = 'mike Taylor'

name_title = name.title() 

print(name_title)
# Mike Taylor

Check if the String starts or ends with a particular character or characters

name = 'Mike'

print(name.startswith('M')) 
# True

print(name.endswith('ke')) 
# True

Replace part of the String with other characters

name = "Mike"

new_name = name.replace('M', 'P')

print(new_name)
# Pike

Return the position of a specific character

name = "Mike"

print(name.find('k'))
# 2

Note that the first position always starts at zero and if the character is not found, the function will return -1

Conclusion

That's all for today, I'll post a new article every other day or so. To make sure you don't miss anything, you can follow me on twitter: Follow @ EricTheCoder_