What Does the U Before String Mean in Python? A Complete Guide for Beginners

7 min readNov 18, 2023

If you are new to Python, you might have come across some strings that have a letter u before them, like this:

u'Hello, world!'

What does this u mean? Why is it there? How does it affect the way you work with strings in Python? In this article, I will answer all these questions and more. I will explain what u stands for, how it relates to Unicode and encoding, and how you can use it in your code. By the end of this article, you will have a clear understanding of the u before a string in Python and how to use it effectively.

What is Unicode and Why Does It Matter?

Before we dive into the u before a string, we need to understand what Unicode is and why it matters. Unicode is a standard that defines a unique number for every character in every language in the world. For example, the letter A has the Unicode number 65, the Chinese character 中 has the Unicode number 20013, and the emoji

has the Unicode number 128522. Unicode allows us to represent any text in any language using a consistent and universal system.

However, Unicode numbers are not very convenient to store and transmit in computers, which use binary digits (bits) to represent data. Therefore, we need a way to convert Unicode numbers into sequences of bits that can be stored and transmitted. This process is called encoding. There are different ways to encode Unicode numbers, such as UTF-8, UTF-16, and UTF-32. Each encoding has its own advantages and disadvantages, such as the number of bits required, the compatibility with different platforms, and the support for different languages.

Python supports Unicode and different encodings, and allows you to work with text in any language. However, depending on the version of Python you are using, the way you handle Unicode and encoding may differ.

How Does Python 2 Handle Unicode and Encoding?

In Python 2, there are two types of strings: regular strings and Unicode strings. Regular strings are sequences of bytes that represent encoded text. For example, the string ‘Hello, world!’ is a sequence of 13 bytes that represent the text in ASCII encoding, which is a subset of UTF-8 encoding. Unicode strings are sequences of Unicode numbers that represent the text directly. For example, the string u’Hello, world!’ is a sequence of 13 Unicode numbers that represent the text in Unicode.

To create a regular string in Python 2, you can use single quotes or double quotes, like this:

s = 'Hello, world!'
s = "Hello, world!"

To create a Unicode string in Python 2, you need to add a u before the quotes, like this.

s = u'Hello, world!'
s = u"Hello, world!"

The u before the string tells Python that the string is a Unicode string, not a regular string. This is important because regular strings and Unicode strings behave differently in Python 2. For example, if you try to concatenate a regular string and a Unicode string, you will get an error, like this:

s1 = 'Hello, '
s2 = u'world!'
s = s1 + s2 # TypeError: cannot concatenate 'str' and 'unicode' objects

This is because Python 2 does not know how to combine bytes and Unicode numbers. To avoid this error, you need to either convert the regular string to a Unicode string, or the Unicode string to a regular string, using the built-in functions unicode() and str(), like this:

s1 = 'Hello, '
s2 = u'world!'
s = unicode(s1) + s2 # u'Hello, world!'
s = s1 + str(s2) # 'Hello, world!'

Another difference between regular strings and Unicode strings in Python 2 is the way they are displayed. When you print a regular string, Python 2 will show the encoded text as it is. When you print a Unicode string, Python 2 will show the Unicode numbers in hexadecimal format, prefixed with \u, like this:

s1 = 'Hello, world!'
s2 = u'Hello, world!'
print(s1) # Hello, world!
print(s2) # u'Hello, world!'

This is because Python 2 does not know how to decode the Unicode numbers into the corresponding characters. To see the actual text, you need to encode the Unicode string using the appropriate encoding, such as UTF-8, like this:

s2 = u'Hello, world!'
print(s2.encode('utf-8')) # Hello, world!

How Does Python 3 Handle Unicode and Encoding?

In Python 3, there is only one type of string: Unicode string. All strings are sequences of Unicode numbers that represent the text directly. There is no need to add a u before the string, because Python 3 assumes that all strings are Unicode strings by default. For example, the string ‘Hello, world!’ is a sequence of 13 Unicode numbers that represent the text in Unicode.

To create a string in Python 3, you can use single quotes or double quotes, like this:

s = 'Hello, world!'
s = "Hello, world!"

There is no difference between single quotes and double quotes in Python 3, except for stylistic preference. You can use either one to create a string, as long as you are consistent.

Python 3 handles Unicode and encoding much more smoothly than Python 2. For example, you can concatenate any strings without worrying about the type, like this:

s1 = 'Hello, '
s2 = 'world!'
s = s1 + s2 # 'Hello, world!'

Python 3 will automatically convert the strings to the same encoding before concatenating them. You can also print any string without encoding it, and Python 3 will show the actual text, like this:

s = 'Hello, world!'
print(s) # Hello, world!

Python 3 will automatically decode the Unicode numbers into the corresponding characters, using the default encoding of your system.

How to Use the U Before a String in Python?

Now that you know what the u before a string means in Python, you might wonder how to use it in your code. The answer depends on the version of Python you are using and the purpose of your code.

If you are using Python 2, you should use the u before a string whenever you want to create a Unicode string, especially if you are working with text in different languages. This will ensure that your code is compatible with Unicode and can handle any text correctly. For example, if you want to create a string that contains the Chinese character 中, you should use the u before the string, like this:

s = u'中'

This will create a Unicode string that contains the Unicode number 20013, which represents the character 中. If you omit the u before the string, you will create a regular string that contains the byte 0xE4, which is the UTF-8 encoding of the character 中, like this:

s = '中'

This will create a regular string that contains the byte 0xE4, which may not be interpreted correctly by Python 2 or other programs. For example, if you try to print this string, you will get an error, like this:

s = '中'
print(s) # UnicodeDecodeError: 'ascii' codec can't decode byte 0xe4 in position 0: ordinal not in range(128)

This is because Python 2 tries to decode the byte 0xE4 using the ASCII encoding, which does not support the character 中. To avoid this error, you need to encode the string using the appropriate encoding, such as UTF-8, like this:

s = '中'
print(s.encode('utf-8')) # 中

However, this is not very convenient and may cause confusion. Therefore, it is better to use the u before the string to create a Unicode string in Python 2.

If you are using Python 3, you do not need to use the u before a string, because all strings are Unicode strings by default. However, you can still use the u before a string if you want to make your code compatible with Python 2. This will not affect the functionality of your code, but it will make it easier to port your code to Python 2 if needed. For example, if you want to create a string that contains the Chinese character 中, you can use the u before the string, like this:

s = u'中'

This will create a Unicode string that contains the Unicode number 20013, which represents the character 中. This is exactly the same as creating a string without the u before the string, like this:

s = '中'

Both strings are identical in Python 3, and you can use them interchangeably. However, the first string will also work in Python 2, while the second string will not. Therefore, using the u before the string can make your code more compatible with both versions of Python.

Conclusion

In this article, I have explained what the u before a string means in Python, how it relates to Unicode and encoding, and how to use it in your code. I hope you have learned something new and useful from this article. Here are some key points:

To recap, the u before a string means that the string is a Unicode string, which is a sequence of Unicode numbers that represent the text directly. Unicode is a standard that defines a unique number for every character in every language in the world. Encoding is the process of converting Unicode numbers into sequences of bits that can be stored and transmitted by computers. There are different ways to encode Unicode numbers, such as UTF-8, UTF-16, and UTF-32.
In Python 2, there are two types of strings: regular strings and Unicode strings. Regular strings are sequences of bytes that represent encoded text. Unicode strings are sequences of Unicode numbers that represent the text directly. To create a Unicode string in Python 2, you need to add a u before the quotes, like this:

s = u'Hello, world!'

In Python 3, there is only one type of string: Unicode string. All strings are sequences of Unicode numbers that represent the text directly. There is no need to add a u before the string, because Python 3 assumes that all strings are Unicode strings by default. However, you can still use the u before a string if you want to make your code compatible with Python 2. For example, the string u’Hello, world!’ is identical to the string ‘Hello, world!’ in Python 3, but not in Python 2.
In this article, I will show you some examples of how to use the u before a string in Python, and how it affects the way you work with strings in different scenarios. I will also give you some tips and best practices on how to handle Unicode and encoding in Python. Let’s get started!