Harness the power of words in Python by manipulating text, also known as strings.

What Are Strings?

In programming, strings are essentially the text data your code uses. This terminology differentiates it from the code itself or comments in your code, which technically is all in a text document anyway.

In Python, you can write strings with either double quotes " " or single quotes ' '. Like other data, it can be stored in variables.

x = "This is a string"

y = 'This is also a valid string'

If you remember the type() function from before you can check the types of these variables.

type(x)

str

str is what Python calls the string type.

You can convert numerical data such as integers and floats into strings by using str().

x = 42
type(x)

int

x

42

x = str(42)
type(x)

str

x

'42'

Notice the quotes around the number 42 in that last output. This is telling us the value of x is now a string.

Introducing the Print Function

Up to this point, we have been viewing the values of variables and output of our code by typing either the variable or expression in a single line in the Jupyter Notebook or ipython terminal. You wouldn't normally do this in programs you write so let's introduce a way to directly tell Python to print some text. The built-in print() function will do this for us.

print("My custom string")

My custom string

print(x)

42

print(your_expression) will print the string representation of the expression to the terminal. Note that x is still a string. Since print always outputs a string, x doesn't have the quotes around it like before.

Adding print statements to your code is useful if you want to see the values of variables at different steps.

def my_function():
    """Example function that doesn't return anything but prints to the terminal"""
    x = 42
    print(x)
    x = x *2
    print(x)

my_function()

42
84

We see that by calling my_function() the print statement outputs the value of x at the point in time print was called.

Escape Characters

Since quotes (either single or double) are special characters used to declare the start and end of a string in your code, you can't use them directly in your strings without the use of a special escape character. The \.

For instance, this won't work:

print("Everyone loves "air quotes"!")

  File "<ipython-input-13-a83c1453fe18>", line 1
    print("Everyone loves "air quotes"!")
                             ^
SyntaxError: invalid syntax

You need to escape the inside quotes you want to use in the value of your string.

print("Everyone loves \"air quotes\"!")

If you declare the string with double quotes, you can use single quotes inside without escaping, and vice versa.

print("Everyone loves 'air quotes'!")

Everyone loves 'air quotes'!

This means declaring strings with double quotes makes using apostrophes ' a little easier.

print("I'm awesome 'cause reasons.")

I'm awesome 'cause reasons.

If you use single quotes, you have to escape the apostrophes.

print('I\'m awesome \'cause reasons.')

I'm awesome 'cause reasons.

Another common use of the escape character is to create strings that have text on multiple lines. \n is the newline character.

print("This sentence is on the first line.\nThis sentence is on the second line.")

This sentence is on the first line.
This sentence is on the second line.

There are other times you may see characters escaped, but we'll discuss those as we come across them.

Triple Quote (Multi-line) Strings

You may recall in some of our functions we created a docstring using triple quotes """ """. You can create strings with triple quotes in normal code. This will automatically include the end of line characters.

print("""First line.
Second line.
    Tabbed. Third line.""")

First line.
Second line.
    Tabbed. Third line.

Manipulating Strings

There are a lot of operations we can perform on strings once we've declared them. Let's go through a few examples.

Calculate how many characters are in a string (the length) by using the len() function.

my_string = "Hello and welcome!"
print(len(my_string))

18

You can add or concatenate two or more strings together by using the + operator.

new_string = my_string + " I hope you are enjoying learning to program."
print(new_string)

Hello and welcome! I hope you are enjoying learning to program.

You can duplicate a string multiple times by using the * operator.

double_me = "Show me twice!"
print(double_me * 2)

Show me twice!Show me twice!

You can break up a string into a list of strings using .split(). We will talk about lists more in a future tutorial.

# Separate the string at each empty space ' '.
print(my_string.split(' '))

['Hello', 'and', 'welcome!']

You can change the case of a string by calling several methods on the string object.

# Convert all character to lowercase.
my_string.lower()

'hello and welcome!'

# Convert all character to uppercase.
my_string.upper()

'HELLO AND WELCOME!'

# Convert to title case.
my_string.title()

'Hello And Welcome!'

Get A String From The User

You can prompt the user to enter a string in the command line or notebook by using the built-in input() function. It will store whatever the user types in the variable you specify.

users_name = input("Enter your name: ")
print(users_name)

Enter your name: Daniel
Daniel

print(users_name)

Daniel

The string you pass to input() is the message displayed to the user.

Sometimes getting input from a user means some unwanted spaces in your string.

users_name = input("Enter your name: ")
users_name

Enter your name:          Daniel      





'         Daniel      '

You can remove the extra whitespace at the start and end of a string by using the .strip() method.

users_name = users_name.strip()
users_name

'Daniel'

This is useful to fix odd inputs you might get from users or other sources of data.

String Formatting

You can format your string with the values of variables in your code. Write a single string, and populate it with a user's name, phone number, age or email for example. Let's look at two methods to do essentially the same thing. First is the .format() method, and then a more recent approach called f-strings available in Python version 3.6 and higher.

Using .format()

formatted_string = "Hello {}! welcome to your homepage.".format(users_name)
print(formatted_string)

Hello Daniel! welcome to your homepage.

Here we declared a string with a placeholder using the curly brackets {}. The value of the first argument to .format() is placed inside the placeholder when the string is printed. You can have multiple placeholders and they will be formatted in the order of the arguments.

formatted_string = "{}, the year is {}, and you love {}.".format(users_name, 2020, "coffee")
print(formatted_string)

Daniel, the year is 2020, and you love coffee.

If you want to use variables multiple times in a string, or with a different order than the arguments passed to .format() you can specify numbers that correspond to the arguments. Staring with 0. (Python is zero-indexed. We'll talk about that more when we come to lists).

formatted_string = "In the beginning there was {2}, {0}. Now, in the year {1}, there is still much {2}".format(users_name, 2020, "coffee")
print(formatted_string)

In the beginning there was coffee, Daniel. Now, in the year 2020, there is still much coffee

You'll notice here we used them out of order, and we used "coffee" twice in the string while only having to pass it as a single argument to .format().

Using f-strings

In Python 3.6 and newer versions, we can use an alternative approach to string formatting called f-strings. You can enter variables and expressions directly into the string's placeholders {} instead of passing them to .format() at the end of the string. Simply put an f before the string when you declare it.

f_string = f"Hello {users_name}! welcome to your homepage."
print(f_string)

Hello Daniel! welcome to your homepage.

You can put expressions inside the placeholders as well.

f_string = f"The product of 3 and 5 is {3 * 5}."
print(f_string)

The product of 3 and 5 is 15.

What happens if we end up with a float in our string?

f_string = f"The answer to 10 divided by 3 is {10/3}."
print(f_string)

The answer to 10 divided by 3 is 3.3333333333333335.

Yikes! That's a lot of decimal places. What if we only want to display the number up to two decimal places? Luckily we can use format specifications to gain more control over how the string is displayed.

f_string = f"The answer to 10 divided by 3 is {10/3:.2f}."
print(f_string)

The answer to 10 divided by 3 is 3.33.

We added this part :.2f to the end of our placeholder. This works for both f-strings and the .format() method. The part after the : is the format specification. Here we say we want a precision of two decimal places (.2) and indicate it is a floating-point number. (f). There are a lot more options to format specifications which we will cover as the need arises. If you're curious you can head on over to the official documentation (opens new window).

Fun with Emoji 😎

Strings are sequences of characters. Since Python 3.0 these sequences are stored as unicode. This was a pretty big advancement from 2.X.

Q: What is Unicode?

A: Unicode is the universal character encoding, maintained by the Unicode Consortium. This encoding standard provides the basis for processing, storage and interchange of text data in any language in all modern software and information technology protocols.

From the FAQ (opens new window) we learn that the Unicode standard is important in ensuring data can be more easily interchanged between any language in modern software. This means you can write strings in Python in the language of your choice!

print("my favorite color is blue.")
print("我最喜欢的颜色是蓝色的")
print("הצבע האהוב עליי הוא כחול")

my favorite color is blue.
我最喜欢的颜色是蓝色的
הצבע האהוב עליי הוא כחול

Here we see Chinese and Hebrew according to Google Translate.

This works well if you are working in a browser, such as Chrome or Firefox. You may have issues with the characters being displayed correctly on the command line, depending on which terminal you're using.

Perhaps the most fun and immediate use of Unicode though is the use of emoji. Take a look at the Full Emoji List (opens new window) from unicode.org. You can select, copy, then paste characters from the Browser column into your code. This is because these are not images, but rather how the browser renders Unicode characters. Go try it out!

x = "💙🚀🌞😈🤯🤬 Having fun yet? 💙🚀🌞😈🤯🤬"
print(x * 2)

💙🚀🌞😈🤯🤬 Having fun yet? 💙🚀🌞😈🤯🤬💙🚀🌞😈🤯🤬 Having fun yet? 💙🚀🌞😈🤯🤬

Review

Let's review what we covered in this tutorial.

• Introduced a new data type called str in Python for strings.
• You can use either single or double quotes to declare strings.
• Introduced the print function to output strings to the terminal.
• How to escape characters such as apostrophes or newlines.
• How to manipulate strings using concatenation, duplication, and methods for changing case.
• Use the input function to get a string from the user and remove extra whitespace.
• Format strings with data from your code using either f-strings or the .format method.
• Introduced the format specification mini-language.
• Learned that strings are stored as Unicode in Python, allowing you to write multi-lingual code and expressive emoji. 💩 (Can you not see how this sentence is enhanced by the use of emoji?!)

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I sincerely hope you enjoyed and learned something from this article. For questions, you can contact me on Twitter (opens new window), for errors or corrections in the article you can create an Issue on GitHub (opens new window). Thanks for reading! 📖

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