Embedded Files
STRNGS
Strings
Strings
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:
Example
Example
print("Hello")
print('Hello')
Assign String to a Variable
Assign String to a Variable
Assigning a string to a variable is done with the variable name followed by an equal sign and the string:
Example
Example
a = "Hello"
print(a)
Multiline Strings
Multiline Strings
You can assign a multiline string to a variable by using three quotes:
Example
Example
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:
Example
Example
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.
Strings are Arrays
Strings are Arrays
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.
Example
Example
Get the character at position 1 (remember that the first character has the position 0):
a = "Hello, World!"
print(a[1])
Looping Through a String
Looping Through a String
Since strings are arrays, we can loop through the characters in a string, with a for loop.
Example
Example
Loop through the letters in the word "banana":
for x in "banana":
print(x)
Learn more about For Loops in our Python For Loops chapter.
String Length
String Length
To get the length of a string, use the len() function.
Example
Example
The len() function returns the length of a string:
a = "Hello, World!"
print(len(a))
Check String
Check String
To check if a certain phrase or character is present in a string, we can use the keyword in.
Example
Example
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:
Example
Example
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.
Check if NOT
Check if NOT
To check if a certain phrase or character is NOT present in a string, we can use the keyword not in.
Example
Example
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:
Example
Example
print only if "expensive" is NOT present:
txt = "The best things in life are free!"
if "expensive" not in txt:
print("Yes, 'expensive' is NOT present.")
SLICING STRING
SLICING STRING
Slicing
Slicing
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.
Example
Example
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.
Slice From the Start
Slice From the Start
By leaving out the start index, the range will start at the first character:
Example
Example
Get the characters from the start to position 5 (not included):
b = "Hello, World!"
print(b[:5])
Slice To the End
Slice To the End
By leaving out the end index, the range will go to the end:
Example
Example
Get the characters from position 2, and all the way to the end:
b = "Hello, World!"
print(b[2:])
Negative Indexing
Negative Indexing
Use negative indexes to start the slice from the end of the string:
Example
Example
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])
MODIFY STRINGS
Upper Case
Upper Case
Example
Example
The upper() method returns the string in upper case:
a = "Hello, World!"
print(a.upper())
Lower Case
Lower Case
Example
Example
The lower() method returns the string in lower case:
a = "Hello, World!"
print(a.lower())
Remove Whitespace
Remove Whitespace
Whitespace is the space before and/or after the actual text, and very often you want to remove this space.
Example
Example
The strip() method removes any whitespace from the beginning or the end:
a = " Hello, World! "
print(a.strip()) # returns "Hello, World!"
Replace String
Replace String
Example
Example
The replace() method replaces a string with another string:
a = "Hello, World!"
print(a.replace("H", "J"))
Split String
Split String
The split() method returns a list where the text between the specified separator becomes the list items.
Example
Example
The split() method splits the string into substrings if it finds instances of the separator:
a = "Hello, World!"
print(a.split(",")) # returns ['Hello', ' World!']
STRING CONCATENATE
String Concatenation
String Concatenation
To concatenate, or combine, two strings you can use the + operator.
Example
Example
Merge variable a with variable b into variable c:
a = "Hello"
b = "World"
c = a + b
print(c)
Example
Example
To add a space between them, add a " ":
a = "Hello"
b = "World"
c = a + " " + b
print(c)
FORMATE STRING
String Format
String Format
As we learned in the Python Variables chapter, we cannot combine strings and numbers like this:
Example
Example
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:
Example
Example
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:
Example
Example
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:
Example
Example
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 CHARACTERS
Escape Character
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:
Example
Example
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 \":
Example
Example
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."
Escape Characters
Escape Characters
Other escape characters used in Python:
Code
Result
Try it
\'
Single Quote
\\
Backslash
\n
New Line
\r
Carriage Return
\t
Tab
\b
Backspace
\f
Form Feed
\ooo
Octal value
\xhh
Hex value
STRING MENTHODS
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
Converts the first character to upper case
Converts string into lower case
Returns a centered string
Returns the number of times a specified value occurs in a string
Returns an encoded version of the string
Returns true if the string ends with the specified value
Sets the tab size of the string
Searches the string for a specified value and returns the position of where it was found
Formats specified values in a string
format_map()
Formats specified values in a string
Searches the string for a specified value and returns the position of where it was found
Returns True if all characters in the string are alphanumeric
Returns True if all characters in the string are in the alphabet
Returns True if all characters in the string are decimals
Returns True if all characters in the string are digits
Returns True if the string is an identifier
Returns True if all characters in the string are lower case
Returns True if all characters in the string are numeric
Returns True if all characters in the string are printable
Returns True if all characters in the string are whitespaces
Returns True if the string follows the rules of a title
Returns True if all characters in the string are upper case
Joins the elements of an iterable to the end of the string
Returns a left justified version of the string
Converts a string into lower case
Returns a left trim version of the string
Returns a translation table to be used in translations
Returns a tuple where the string is parted into three parts
Returns a string where a specified value is replaced with a specified value
Searches the string for a specified value and returns the last position of where it was found
Searches the string for a specified value and returns the last position of where it was found
Returns a right justified version of the string
Returns a tuple where the string is parted into three parts
Splits the string at the specified separator, and returns a list
Returns a right trim version of the string
Splits the string at the specified separator, and returns a list
Splits the string at line breaks and returns a list
Returns true if the string starts with the specified value
Returns a trimmed version of the string
Swaps cases, lower case becomes upper case and vice versa
Converts the first character of each word to upper case
Returns a translated string
Converts a string into upper case
Fills the string with a specified number of 0 values at the beginning
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