Strings in python are surrounded by either single quotation marks, or double quotation marks.
'hello' is the same as "hello".
You can display a string literal with the print() function:
print("Hello")
print('Hello')
Assigning a string to a variable is done with the variable name followed by an equal sign and the string:
a = "Hello"
print(a)
You can assign a multiline string to a variable by using three quotes:
You can use three double quotes:
a = """Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do
eiusmod tempor incididunt
ut labore et dolore magna aliqua."""
print(a)
Or three single quotes:
a = '''Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do
eiusmod tempor incididunt
ut labore et dolore magna aliqua.'''
print(a)
Note: in the result, the line breaks are inserted at the same position as in the code.
Like many other popular programming languages, strings in Python are arrays of bytes representing unicode characters.
However, Python does not have a character data type, a single character is simply a string with a length of 1.
Square brackets can be used to access elements of the string.
Get the character at position 1 (remember that the first character has the position 0):
a = "Hello, World!"
print(a[1])
Since strings are arrays, we can loop through the characters in a string, with a for loop.
Loop through the letters in the word "banana":
for x in "banana":
print(x)
You will learn more about for loops in our Python For Loops chapter.
To get the length of a string, use the len() function.
The len() function returns the length of a string:
a = "Hello, World!"
print(len(a))
To check if a certain phrase or character is present in a string, we can use
the keyword
in.
Check if "free" is present in the following text:
txt = "The best things in life are free!"
print("free" in txt)
Use it in an if statement:
Print only if "free" is present:
txt = "The best things in life are free!"
if "free" in txt:
print("Yes, 'free' is present.")
Learn more about If statements in our Python If...Else chapter.
To check if a certain phrase or character is NOT present in a string, we can use
the keyword not in.
Check if "expensive" is NOT present in the following text:
txt = "The best things in life are free!"
print("expensive" not in txt)
Use it in an if statement:
print only if "expensive" is NOT present:
txt = "The best things in life are free!"
if "expensive" not in txt:
print("No, 'expensive' is NOT present.")
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.
Get the characters from position 2 to position 5 (not included):
b = "Hello, World!"
print(b[2:5])
Note: The first character has index 0.
By leaving out the start index, the range will start at the first character:
Get the characters from the start to position 5 (not included):
b = "Hello, World!"
print(b[:5])
By leaving out the end index, the range will go to the end:
Get the characters from position 2, and all the way to the end:
b = "Hello, World!"
print(b[2:])
Get the characters:
From: "o" in "World!" (position -5)
To, but not included: "d" in "World!" (position -2):
b = "Hello, World!"
print(b[-5:-2])
Python has a set of built-in methods that you can use on strings.
The upper() method returns the string in upper case:
a = "Hello, World!"
print(a.upper())
The lower() method returns the string in lower case:
a = "Hello, World!"
print(a.lower())
Whitespace is the space before and/or after the actual text, and very often you want to remove this space.
The strip() method removes any whitespace from the beginning or the end:
a = " Hello, World! "
print(a.strip()) # returns "Hello, World!"
The replace() method replaces a string with another string:
a = "Hello, World!"
print(a.replace("H", "J"))
The split() method returns a list where the text between the specified separator becomes the list items.
The split() method splits the string into substrings if it finds instances of the separator:
a = "Hello, World!"
print(a.split(",")) #
returns ['Hello', ' World!']
Learn more about Lists in our Python Lists chapter.
To concatenate, or combine, two strings you can use the + operator.
Merge variable a with variable
b into variable c:
a = "Hello"
b = "World"
c = a + b
print(c)
To add a space between them, add a " ":
a = "Hello"
b = "World"
c = a + " " + b
print(c)
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:
Use the format() method to insert numbers
into strings:
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))
Learn more about String Formatting in our String Formatting chapter.
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:
You will get an error if you use double quotes inside a string that is surrounded by double quotes:
txt = "We are the so-called "Vikings" from the north."
To fix this problem, use the escape character \":
The escape character allows you to use double quotes when you normally would not be allowed:
txt = "We are the so-called \"Vikings\" from the north."
Other escape characters used in Python:
| Code | Result | |
|---|---|---|
| \' | Single Quote | |
| \\ | Backslash | |
| \n | New Line | |
| \r | Carriage Return | |
| \t | Tab | |
| \b | Backspace | |
| \f | Form Feed | |
| \ooo | Octal value | |
| \xhh | Hex value |
Python has a set of built-in methods that you can use on strings.
Note: All string methods returns new values. They do not change the original string.
| Method | Description |
|---|---|
| capitalize() | Converts the first character to upper case |
| casefold() | Converts string into lower case |
| center() | Returns a centered string |
| count() | Returns the number of times a specified value occurs in a string |
| encode() | Returns an encoded version of the string |
| endswith() | Returns true if the string ends with the specified value |
| expandtabs() | Sets the tab size of the string |
| find() | Searches the string for a specified value and returns the position of where it was found |
| format() | Formats specified values in a string |
| format_map() | Formats specified values in a string |
| index() | Searches the string for a specified value and returns the position of where it was found |
| isalnum() | Returns True if all characters in the string are alphanumeric |
| isalpha() | Returns True if all characters in the string are in the alphabet |
| isdecimal() | Returns True if all characters in the string are decimals |
| isdigit() | Returns True if all characters in the string are digits |
| isidentifier() | Returns True if the string is an identifier |
| islower() | Returns True if all characters in the string are lower case |
| isnumeric() | Returns True if all characters in the string are numeric |
| isprintable() | Returns True if all characters in the string are printable |
| isspace() | Returns True if all characters in the string are whitespaces |
| istitle() | Returns True if the string follows the rules of a title |
| isupper() | Returns True if all characters in the string are upper case |
| join() | Joins the elements of an iterable to the end of the string |
| ljust() | Returns a left justified version of the string |
| lower() | Converts a string into lower case |
| lstrip() | Returns a left trim version of the string |
| maketrans() | Returns a translation table to be used in translations |
| partition() | Returns a tuple where the string is parted into three parts |
| replace() | Returns a string where a specified value is replaced with a specified value |
| rfind() | Searches the string for a specified value and returns the last position of where it was found |
| rindex() | Searches the string for a specified value and returns the last position of where it was found |
| rjust() | Returns a right justified version of the string |
| rpartition() | Returns a tuple where the string is parted into three parts |
| rsplit() | Splits the string at the specified separator, and returns a list |
| rstrip() | Returns a right trim version of the string |
| split() | Splits the string at the specified separator, and returns a list |
| splitlines() | Splits the string at line breaks and returns a list |
| startswith() | Returns true if the string starts with the specified value |
| strip() | Returns a trimmed version of the string |
| swapcase() | Swaps cases, lower case becomes upper case and vice versa |
| title() | Converts the first character of each word to upper case |
| translate() | Returns a translated string |
| upper() | Converts a string into upper case |
| zfill() | Fills the string with a specified number of 0 values at the beginning |