How to Read in Consonants in Python
And so we've seen numbers, merely what about text? This page is about the Python string, which is the go-to Python information type for storing and using text in Python. So, in Python, a slice of text is chosen a string and you can perform all kinds of operations on a string. But allow's start with the nuts showtime!
What is a Python string?
The following is a formal definition of what a cord is:
- Cord
- A string in Python is a sequence of characters
In even simpler terms, a string is a piece of text. Strings are not merely a Python affair. It's a well-known term in the field of computer science and means the same matter in virtually other languages likewise. At present that we know what a string is, we'll expect at how to create a string.
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How to create a Python string
A Python string needs quotes around it for it to exist recognized as such, like this:
>>> 'Hello, World' 'Hello, World'
Because of the quotes, Python understands this is a sequence of characters and not a command, number, or variable.
And just like with numbers, some of the operators we learned before work on Python strings too. Try it with the following expressions:
>>> 'a' + 'b' 'ab' >>> 'ab' * 4 'abababab' >>> 'a' - 'b' Traceback (almost contempo call last): File "<stdin>", line i, in <module> TypeError: unsupported operand type(s) for -: 'str' and 'str'
This is what happens in the lawmaking above:
- The plus operator glues two Python strings together.
- The multiplication operator repeats our Python cord the given number of times.
- The minus operator doesn't work on a Python string and produces an error. If you want to remove parts of a cord, there are other methods that you'll acquire about afterwards on.
Single or double quotes?
We've used single quotes, but Python accepts double-quotes around a string also:
>>> "a" + "b" 'ab'
Note that these are not two single quotes next to each other. It'south the grapheme that's often found next to the enter fundamental on your keyboard. You need to press shift together with this key to get a double quote.
As you tin can come across from its answer, Python itself seems to adopt single quotes. Information technology looks more clear, and Python tries to be as clear and well readable as it can. So why does it support both? It'due south because it allows you to utilize strings that contain a quote.
In the first example beneath, we apply double quotes. Hence there'southward no trouble with the unmarried quote in the word it's. However, in the second instance, we try to use unmarried quotes. Python sees the quote in the discussion it's and thinks this is the stop of the string! The following letter, "s", causes a syntax error. A syntax error is a character or string incorrectly placed in a command or education that causes a failure in execution.
In other words, Python doesn't understand the s at that spot, considering it expects the string to exist ended already, and fails with an error:
>>> mystring = "Information technology's a string, with a single quote!" >>> mystring = 'It's a string, with a single quote!' File "<stdin>", line i mystring = 'Information technology's a string, with a single quote!' ^ SyntaxError: invalid syntax
Every bit you can meet, fifty-fifty the syntax highlighter on the code cake above gets confused! And as you can too see, Python points out the exact location of where information technology encountered the error. Python errors tend to be very helpful, so look closely at them and yous'll ofttimes be able to pinpoint what's going wrong.
Escaping
There's actually another way around this trouble, called escaping. Y'all tin can escape a special character, like a quote, with a astern slash:
>>> mystring = 'Information technology\'s an escaped quote!' >>> mystring "It'due south an escaped quote!"
Y'all can also escape double quotes inside a double-quoted string:
>>> mystring = "I'm a and then-called \"script kiddie\"" >>> mystring 'I\'thou a and then-called "script kiddie"'
Here, over again, you see Python'southward preference for single quotes strings. Even though we used double quotes, Python echos the string back to united states using unmarried quotes. It'due south still the same cord though, it's but represented differently. In one case you start printing strings to the screen, you lot'll run across the evidence of this.
So which one should you lot use? It'south simple: ever opt for the option in which yous need the least amount of escapes because these escapes make your Python strings less readable.
Multiline strings
Python also has syntax for creating multiline strings, using triple quotes. By this I mean three double quotes or three single quotes, both work but I'll demonstrate with double quotes:
>>> my_big_string = """This is line ane, ... this is line ii, ... this is line three."""
The nice thing hither is that y'all can use both single and double quotes within a multiline cord. So you tin can use triple quotes to cleanly create strings that contain both single and double quotes:
>>> line = """He said: "How-do-you-do, I've got a question" from the audition"""
String operations
Strings come with a number of handy, built-in operations you can execute. I'll show you only a couple here since I don't desire to divert your attention from the tutorial too much.
In the REPL, you tin can utilise auto-completion. In the side by side code fragment, nosotros create a string, mystring, and on the next line we type its name followed past hitting the <TAB> key twice:
>>> mystring = "Howdy globe" >>> mystring. mystring.capitalize( mystring.find( mystring.isdecimal( mystring.istitle( mystring.partition( mystring.rstrip( mystring.translate( mystring.casefold( mystring.format( mystring.isdigit( mystring.isupper( mystring.supplant( mystring.split( mystring.upper( mystring.center( mystring.format_map( mystring.isidentifier( mystring.join( mystring.rfind( mystring.splitlines( mystring.zfill( mystring.count( mystring.index( mystring.islower( mystring.ljust( mystring.rindex( mystring.startswith( mystring.encode( mystring.isalnum( mystring.isnumeric( mystring.lower( mystring.rjust( mystring.strip( mystring.endswith( mystring.isalpha( mystring.isprintable( mystring.lstrip( mystring.rpartition( mystring.swapcase( mystring.expandtabs( mystring.isascii( mystring.isspace( mystring.maketrans( mystring.rsplit( mystring.title(
If all went well, you should get a large list of operations that tin be performed on a string. You can attempt some of these yourself:
>>> mystring.lower() 'how-do-you-do world' >>> mystring.upper() 'HELLO WORLD'
An explanation of each of these operations can exist found in the official Python documentation, but we'll cover a few here also.
Getting the cord length
A common operation is to get the string length. Unlike the operations above, this can exist done with Python'southward len() function like this:
>>> len("I wonder how long this cord volition be...") forty >>> len(mystring) 11 In fact, the len() function can exist used on many objects in Python, as y'all'll learn later on. If functions are new to you, you're in luck, because our adjacent page will explain exactly what a function in Python is, and how you tin create ane yourself.
Separate a string
Another common operation is splitting a cord. For this, nosotros tin use one of the born operations, conveniently called split. Allow'south start simple, by splitting up two words on the space character between them:
'Hello world'.split(' ') ['Hullo', 'globe'] The separate operation takes one statement, which is the sequence of characters to split on. The output is a Python list, containing all the dissever words.
Dissever on whitespace
A common use-case is to divide on whitespace. The problem is that whitespace can be a lot of things. Three common ones that you lot probably know already are:
- space characters
- tabs
- newlines
But there are many more, and to make it even more complicated, whitespace doesn't mean just 1 of these characters, but can also exist a whole sequence of them. E.g., three consecutive spaces and a tab character course one piece of whitespace.
Exactly because this is such a mutual operation amid programmers, and because it'southward hard to practice it perfectly, Python has a user-friendly shortcut for information technology. Calling the split operation without any arguments splits a string on whitespace, every bit can exist seen beneath:
>>> 'Hello \t\n there,\t\t\t stranger.'.split() ['Hello', 'at that place,', 'stranger.']
Equally you can see, no thing what whitespace character and how many, Python is withal able to split this cord for us into separate words.
Replace parts of a string
Allow'due south wait at one more congenital-in operation on strings: the supplant function. Information technology's used to supervene upon one or more characters or sequences of characters:
>>> 'Hullo earth'.supercede('H', 'h') 'hello world' >>> 'Hello world'.replace('50', '_') 'He__o wor_d >>> 'Hello world'.supervene upon('world', 'readers') 'Hello readers' Reversing a string
A mutual assignment is to reverse a Python string. There'south no opposite performance, though, as y'all might have noticed when studying the list of operations similar lower() and upper() that comes with a cord. This is not exactly beginner stuff, and then experience free to skip this for now if you're going through the tutorial sequentially.
To reverse a string efficiently, we can treat a string every bit a list. Lists are covered later on in this tutorial (meet for-loop). In fact, you could see a string equally a listing of characters. And, more chiefly, you can care for information technology every bit such. List alphabetize operations like mystring[2] work just similar they work on lists:
>>> mystring = 'Hello world' >>> mystring[2] 'fifty' >>> mystring[0] 'H'
Notation that in Python, like in all reckoner languages, nosotros kickoff counting from 0.
What also works exactly the same as in lists, is the slicing operator. Details of list slicing tin be establish on the Python list folio and won't be repeated hither. If you're coming from other languages, you might compare it to an operation similar substring() in Java, which allows you lot to think specific parts of a string.
Slicing in Python works with the slicing operator, which looks like this: mystring[get-go:stop:step_size]. The central characteristic nosotros use from slicing is the step size. Past giving the slicing operator a negative pace size of -ane, nosotros traverse the string from stop to get-go. By leaving the get-go and end position empty, Python assumes with desire to slice the unabridged string.
So we can employ slicing to reverse a Python string equally follows:
>>> mystring = 'Hello world' >>> mystring[::-1] 'dlrow olleH'
Python string format with f-strings
A common pattern is the need to merge some text strings together or utilise a variable within your string. There are several ways to do so, simply the most mod way is to utilize f-strings, short for formatted strings.
Let's first look at an example, before we swoop into the details:
>>> my_age = twoscore >>> f'My age is {my_age}' My age is 40 The f-cord looks like a regular string with the improver of an f prefix. This f tells Python to scan the string for curly braces. Within these curly braces, nosotros can put any Python expression we desire. In the above example, nosotros only included the variable my_age. F-strings provide an elegant fashion of including the results of expressions inside strings.
Hither are a couple more than examples you can effort for yourself as well, within the REPL:
>>> f'3 + 4 = {three+4}' '3 + 4 = 7' >>> my_age = 40 >>> f'My age is, unfortunately, not {my_age-viii}' 'My age is, unfortunately, non 32' I'm only touching the basics here. If you're following the tutorial forepart to back, you can go along with the side by side topic since yous know more enough for now. If y'all'd like to detect out more almost f-strings, try the following resource:
- Official docs on f-strings
- The official guide has some more than examples here: formatted string literals
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Source: https://python.land/introduction-to-python/strings
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