How to store string in python
When Python wants to store text in a variable, it creates a variable called a string. Katie Cunningham shows you how to create, print and format strings and when to use strings in the real world. Show
This chapter is from the book When Python wants to store text in a variable, it creates a variable called a string. A string’s sole purpose is to hold text for the program. It can hold anything—from nothing at all (") to enough to fill up all the memory on your computer. Creating StringsCreating a string in Python is very similar to how we stored numbers in the last hour. One difference, however, is that we need to wrap the text we want to use as our string in quotes. Open your Python shell and type in the following: >>> s = "Hello, world" >>> s 'Hello, world' The quotes can be either single (′) or double ("). Keep in mind, though, that if you start with a double quote, you need to end with a double quote (and the same goes for single quotes). Mixing them up only confuses Python, and your program will refuse to run. Look at the following code, where the text “Harold” starts with a double quote but ends with a single quote: >>> name = "Harold' File " As you can see, we got an error. We have to make the quote types match: >>> name = "Harold" >>> name 'Harold' >>> name2 = 'Harold' 'Harold' I have a python string with newlines represented like this:
I want to store the string in a variable but with the \n and \t converted into newlines and tabs:
The reason is because I'm using it in a command that I'm formatting and if I use .format(string) then it formats the command with the \n instead of the actual new line
depperm 9,7214 gold badges42 silver badges64 bronze badges asked Feb 23, 2017 at 18:31
In a string literal, \t and \n normally are replaced the the tab and newline characters. To see that, however, you need to print the string as it is, not its representation. Interactive echo prints the representation.
answered Feb 23, 2017 at 18:48
Terry Jan ReedyTerry Jan Reedy 17.6k1 gold badge39 silver badges51 bronze badges You need to do something like that
answered Feb 23, 2017 at 18:36
Software Carpentry: Storing Multiple Values in ListsThis lesson “Storing Multiple Values in Lists” is lesson 03 from Software Carpentry (“Programming with Python” 2016). Overview:Questions
Objectives
Key points summary
Just as a for loop is a way to do operations many times, a list is a way to store many values. Unlike NumPy arrays, lists are built into the language (so we don’t have to load a library to use them). Creating a list:We create a list by putting values inside square brackets:
List indexBy now we know that Python likes to start counting with zero In the same way, items in the list are indexed starting with zero
and if we loop over a list, the loop variable is assigned elements one at a time:
There is one important difference between lists and strings: we can change the values in a list, but we cannot change individual characters in a string. For example: Changing values of list itemThere is one important difference between lists and strings: we can change the values in a list, but we cannot change individual characters in a string. For example: Within the list we can change one of the elements with a new value. In this case we will substitute the second element on the list (therefore indexed as
The
replacement of element Therefore a list is said to be mutable. On the other hand, if we have a variable called
Therefore a variable is said to be immutable. Mutable or immutableCh-Ch-Ch-Changes Data which can be modified in place is called mutable, while data which cannot be modified is called immutable.
This does not mean that variables with string or number values are constants, but when we want to change the value of a string or number variable, we can only replace the old value with a completely new value.
Lists and arrays, on the other hand, are mutable: we can modify them after they have been created. We can change individual elements, append new elements, or reorder the whole list. For some operations, like sorting, we can choose whether to use a function that modifies the data in place or a function that returns a modified copy and leaves the original unchanged. Be careful when modifying data in place. If two variables refer to the same list, and you modify the list value, it will change for both variables! If you want variables with mutable values to be independent, you must make a copy of the value when you assign it. Because of pitfalls like this, code which modifies data in place can be more difficult to understand. However, it is often far more efficient to modify a large data structure in place than to create a modified copy for every small change. You should consider both of these aspects when writing your code. Nested listsSince lists can contain any Python variable, it can even contain other lists. For example, we could represent the products in the shelves of a small grocery shop, and we could then use an indexing method (starting with
This image provided by Hadley Wickham gives a visual example of the ideas of list and sublists we just explored: Figure 1.Illustration of lists, and idexed items. Modifying a list: append, del, reverseappend() (add) to an existing list:Let’s recreate the We encounter again the “dot notation” that we have seen previously with library commands properties. The command structure is based on properties of lists predefined wihtin
Python. In other words, a Python list by nature has inherent properties that you can list with the
Note: Another method to add an item at the end of the list is by using the
del delete an item:The method to remove an item uses command Let’s redeclare the longer
The item can also be in the middle of the list, for example the 3rd element (therefore index
Reversing a list with reverse()Here again the method uses a “dot notation” method as part of an inherent property of a Python list (use We start again with a renewed
Causing troubleWhile modifying in place, it is useful to remember that Python treats lists in a slightly counter-intuitive way. If we make a list and (attempt to) copy it then modify in place, we can cause all sorts of trouble. In the code below we create the list In doing so, the original
Therefore we inadvertantly added This is because Python stores a list in memory, and then can use multiple names to refer to the same list. See the next paragraph for the safe way to copy a list. Copy a simple list safelyIf all we want to do is copy a (simple) list, we can use the list function, so we do not modify a list we did not mean to. The difference is that rather than writing
In this case the original list This is different from how variables worked in lesson 1, and more similar to how a spreadsheet works. Test your understanding:Turn a String Into a ListUse a for-loop to convert the string “hello” into a list of letters:
Hint: You can create an empty list like this: The provided solution does the following:
What could be improved or changed?
We could go even further in abstraction and use one more variable
Note: using Slicing (subsetting) a listSubsets of lists and strings can be accessed by specifying ranges of values in brackets, similar to how we accessed ranges of positions in a Numpy array. This is commonly referred to as “slicing” the list/string. The code below shows slicing methods for a variable The next segment takes the other portion of the variable, from positions The next segment makes a subset of a list, starting at position The last segment prints the last item from a list with
position
Exercise: Slicing From the EndUse slicing to access only the last four characters of a string or entries of a list.
Would your solution work regardless of whether you knew beforehand the length of the string or list (e.g. if you wanted to apply the solution to a set of lists of different lengths)? If not, try to change your approach to make it more robust. Exercise: Non-continuous slicesSo far we’ve seen how to use slicing to take single blocks of successive entries from a sequence. But what if we want to take a subset of entries that aren’t next to each other in the sequence? You can achieve this by providing a third argument to the range within the brackets, called the step size. The example below shows how you can take every third entry in a list:
Notice that the slice taken begins with the first entry in the range, followed by entries taken at equally-spaced intervals (the steps) thereafter. If you wanted to begin the subset with the third entry, you would need to specify that as the starting point of the sliced range:
Use the step size argument to create a new string that contains only every other character in the string “In an octopus’s garden in the shade”
If you want to take a slice from the beginning of a sequence, you can omit the first index in the range:
And similarly, you can omit the ending index in the range to take a slice to the very end of the sequence:
Exercise: Exchanges
Compare to:
Do they always do the same thing? Which do you find easier to read? Exercise: Overloading
Choose one output from the list:
The technical term for this is operator overloading: a single operator, like How do you store string variables?Here are some more examples of storing strings into variables: string lastName = "Smith"; string book = "Second Foundation"; string foo = "blah"; It is important to note that the variable name can be anything you want as long as it does not contain any spaces.
Where are Python strings stored?CPython stores strings as sequences of unicode characters. Unicode characters are stored with either 1, 2, or 4 bytes depending on the size of their encoding. Byte size of strings increases proportionally with the size of its largest character, since all characters must be of the same size.
How do I store multiple strings in Python?We can do this in many ways.. append() We can append values to the end of the list. We use the append() method for this. ... . insert() You can insert values in a list with the insert() method. Here, you specify a value to insert at a specific position. ... . extend() extend() can add multiple items to a list. Learn by example:. How strings are stored internally in Python?Answer: How are strings stored internally in Python 3? They are stored internally as a Unicode sequence with a know codec. That means that they are a sequence of bytes where each character might be one, two, three or four bytes depending on which Unicode page this characters are from.
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