Type hints cheat sheet (Python 3) Variables; Built-in types; Functions; When you’re puzzled or when things are complicated; Standard “duck types” Classes; Coroutines and asyncio; Miscellaneous; Decorators; Type hints cheat sheet (Python 2) Type system reference. Built-in types; Type inference and type annotations; Kinds of. We created this Python 3 Cheat Sheet initially for students of Complete Python Developer in 2021: Zero to Mastery but we're now sharing it with any Python beginners to help them learn and remember common Python syntax and with intermediate and advanced Python developers as a handy reference. If you'd like to download a PDF version of this Python Cheat Sheet, enter your email below and we'll. Python Coding Cheat Sheet Programming isn’t easy, especially if you’re not good at memorization. Depending on the language you are working with, you must recall a fair share of syntax, commands, and functions. Even if you work with code every day, it’s information that’s easy to forget. Python for Data Science Cheat Sheets. Python is one of the most widely used programming languages in the data science field.Python has many packages and libraries that are specifically tailored for certain functions, including pandas, NumPy, scikit-learn, Matplotlib, and SciPy.The most appealing quality of Python is that anyone who wants to learn it, even beginners, can do so quickly and easily.
By Alex Yang, Dataquest
This cheat sheet is based on Python 3’s documentation on regular expressions. If you're interested in learning Python, we have a free Python Programming: Beginner course for you to try out.
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Special Characters
^ | Matches the expression to its right at the start of a string. It matches every such instance before each n in the string.
$ | Matches the expression to its left at the end of a string. It matches every such instance before each n in the string.
. | Matches any character except line terminators like n.
| Escapes special characters or denotes character classes.
A|B | Matches expression A or B. If A is matched first, B is left untried.
+ | Greedily matches the expression to its left 1 or more times.
* | Greedily matches the expression to its left 0 or more times.
? | Greedily matches the expression to its left 0 or 1 times. But if ? is added to qualifiers (+, *, and ? itself) it will perform matches in a non-greedy manner.
{m} | Matches the expression to its left m times, and not less.
{m,n} | Matches the expression to its left m to n times, and not less.
{m,n}? | Matches the expression to its left m times, and ignores n. See ? above.
Character Classes (a.k.a. Special Sequences)
w | Matches alphanumeric characters, which means a-z, A-Z, and 0-9. It also matches the underscore, _.
d | Matches digits, which means 0-9.
D | Matches any non-digits.
s | Matches whitespace characters, which include the t, n, r, and space characters.
S | Matches non-whitespace characters.
b | Matches the boundary (or empty string) at the start and end of a word, that is, between w and W.
B | Matches where b does not, that is, the boundary of w characters.
A | Matches the expression to its right at the absolute start of a string whether in single or multi-line mode.
Z | Matches the expression to its left at the absolute end of a string whether in single or multi-line mode.
Sets
[ ] | Contains a set of characters to match.
Python Regular Expression Pdf
[amk] | Matches either a, m, or k. It does not match amk.
[a-z] | Matches any alphabet from a to z.
[a-z] | Matches a, -, or z. It matches - because escapes it.
[a-] | Matches a or -, because - is not being used to indicate a series of characters.
[-a] | As above, matches a or -.
[a-z0-9] | Matches characters from a to z and also from 0 to 9.
[(+*)] | Special characters become literal inside a set, so this matches (, +, *, and ).
[^ab5] | Adding ^ excludes any character in the set. Here, it matches characters that are not a, b, or 5.
Groups
( ) | Matches the expression inside the parentheses and groups it.
(? ) | Inside parentheses like this, ? acts as an extension notation. Its meaning depends on the character immediately to its right.
(?PAB) | Matches the expression AB, and it can be accessed with the group name.
(?aiLmsux) | Here, a, i, L, m, s, u, and x are flags:
a— Matches ASCII onlyi— Ignore caseL— Locale dependentm— Multi-lines— Matches allu— Matches unicodex— Verbose
(?:A) | Matches the expression as represented by A, but unlike (?PAB), it cannot be retrieved afterwards.
(?#...) | A comment. Contents are for us to read, not for matching.
A(?=B) | Lookahead assertion. This matches the expression A only if it is followed by B.
A(?!B) | Negative lookahead assertion. This matches the expression A only if it is not followed by B.
(?<=B)A | Positive lookbehind assertion. This matches the expression A only if B is immediately to its left. This can only matched fixed length expressions.
Python Regex List
(?<!B)A | Negative lookbehind assertion. This matches the expression A only if B is not immediately to its left. This can only matched fixed length expressions.
(?P=name) | Matches the expression matched by an earlier group named “name”.
(...)1 | The number 1 corresponds to the first group to be matched. If we want to match more instances of the same expresion, simply use its number instead of writing out the whole expression again. We can use from 1 up to 99 such groups and their corresponding numbers.
Popular Python re module Functions
Python Re Module Cheat Sheet
re.findall(A, B) | Matches all instances of an expression A in a string B and returns them in a list.
re.search(A, B) | Matches the first instance of an expression A in a string B, and returns it as a re match object.
re.split(A, B) | Split a string B into a list using the delimiter A.
re.sub(A, B, C) | Replace A with B in the string C.
Useful Regular Expressions Sites for Python users
Bio: Alex Yang is a writer fascinated by the things code can do. He also enjoys citizen science and new media art.
Original. Reposted with permission.
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