This week I was fixing a bug in a small C# method and wondered how I could do the same string manipulations in Python. Strings seem so simple, but there are many exciting details that are easy to overlook. Therefore, this post dives into strings and how we can manipulate them.
This post is part of my journey to learn Python. You can find the other parts of this series here.
Creating Strings
Strings are immutable sequences of Unicode characters – meaning strings cannot be changed after you created them. You can create a string using '' or "", you just need to end the string in the same way as you started it:
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>>> 'This is a string' 'This is a string' >>> "another string" 'another string' |
Using "" to define the string allows you to use ' inside without the need to escape it:
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>>> "Let's do it" "Let's do it" |
(If you look closely, you notice the returned strings changed from '' to "" between the two last examples. The Python REPL translates the return values to the simplest form to represent strings).
With ''' or """ we can create a multiline string:
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>>> >>> """This is ... a multiline ... string""" 'This is\na multiline\nstring' >>> '''another ... multiline ... string''' 'another\nmultiline\nstring' |
The \n is an escape sequence for a newline. You can find the complete list of all escape sequences in the documentation. Thanks to universal newlines in Python, we can write \n on Windows, Linux and Mac and Python will translate it to the correct form in the operating system expects (see PEP 278).
A raw string starts with an r in front and allows you to skip the escape sequences:
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>>> >>> path = r'c:\temp\myfile' >>> print(path) c:\temp\myfile >>> path 'c:\\temp\\myfile' |
Getting help with strings
The data type of string is str. To get the extensive help and a list of all methods you can use on strings you can type this (use the letter q to quit):
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>>> help(str) Help on class str in module builtins: class str(object) | str(object='') -> str | str(bytes_or_buffer[, encoding[, errors]]) -> str | | Create a new string object from the given object. If encoding or... |
Formatting strings
Strings are immutable, but often we need to get a string that is based on a template. The format function allows us to use these templates and replace the parts we need to customize:
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>>> name = "Johnny" >>> pc = "ZenBook" >>> "Hi {0}, thanks for using {1}".format(name, pc) 'Hi Johnny, thanks for using ZenBook' |
With the format function you can create strings exactly as you need them. However, this flexibility comes with the price of complexity. To use it well you should check the documentation and play with the examples.
With Python 3.6 and newer you can use string interpolation. You must prefix your string with an f and then put the name of your variables between the {} (see PEP 498):
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>>> f"Hi {name}, thanks for using {pc}" 'Hi Johnny, thanks for using ZenBook' |
I use this style a lot in C# and I am happy that this works in Python the same way.
Next
With the basic data structures covered, it is time to take a closer look to control structures and the important role of whitespaces.
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