Python String Operations

You can return a range of characters by using the slice syntax.

Specify the start index and the end index, separated by a colon, to return a part of the string.

b = "Hello, World!"
print(b[2:5])

Slice From the Start

By leaving out the start index, the range will start at the first character:

b = "Hello, World!"
print(b[:5])

Slice To the End

By leaving out the end index, the range will go to the end:

b = "Hello, World!"
print(b[2:])

Negative Indexing

Use negative indexes to start the slice from the end of the string:

b = "Hello, World!"
print(b[-5:-2])

Upper Case

a = "Hello, World!"
print(a.upper())

Lower Case

a = "Hello, World!"
print(a.lower())

Remove Whitespace

Whitespace is the space before and/or after the actual text, and very often you want to remove this space.

a = " Hello, World! "
print(a.strip()) # returns "Hello, World!"

Replace String

a = "Hello, World!"
print(a.replace("H", "J"))

Split String

The split() method returns a list where the text between the specified separator becomes the list items.

a = "Hello, World!"
print(a.split(",")) # returns ['Hello', ' World!']

String Concatenation

To concatenate, or combine, two strings you can use the + operator.

a = "Hello"
b = "World"
c = a + b
print(c)

a = "Hello"
b = "World"
c = a + " " + b
print(c)

String Format

As we learned in the Python Variables chapter, we cannot combine strings and numbers like this:

age = 36
txt = "My name is John, I am " + age
print(txt)

But we can combine strings and numbers by using the format() method!

The format() method takes the passed arguments, formats them, and places them in the string where the placeholders {} are:

age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))

The format() method takes unlimited number of arguments, and are placed into the respective placeholders:

quantity = 3
itemno = 567
price = 49.95
myorder = "I want {} pieces of item {} for {} dollars."
print(myorder.format(quantity, itemno, price))

You can use index numbers {0} to be sure the arguments are placed in the correct placeholders:

quantity = 3
itemno = 567
price = 49.95
myorder = "I want to pay {2} dollars for {0} pieces of item {1}."
print(myorder.format(quantity, itemno, price))

Escape Character

To insert characters that are illegal in a string, use an escape character.

An escape character is a backslash \ followed by the character you want to insert.

An example of an illegal character is a double quote inside a string that is surrounded by double quotes:

txt = "We are the so-called "Vikings" from the north."

Escape Characters

Other escape characters used in Python:

String Methods

Python has a set of built-in methods that you can use on strings.