@ -204,7 +204,7 @@ pre.prettyprint {
< br > < h2 id = "toc" > < a href = "#toc" name = "toc" > #< / a > Contents< / h2 >
< pre > < code class = "hljs bash" > < strong > ToC< / strong > = {
< strong > < span class = "hljs-string" > < span class = "hljs-string" > '1. Collections'< / span > < / span > < / strong > : [< a href = "#list" > List< / a > , < a href = "#dictionary" > Dict< / a > , < a href = "#set" > Set< / a > , < a href = "#range" > Range< / a > , < a href = "#enumerate" > Enumerate< / a > , < a href = "#namedtuple" > Namedtupl e< / a > , < a href = "#iterator" > Iterator< / a > , < a href = "#generator" > Generator< / a > ],
< strong > < span class = "hljs-string" > < span class = "hljs-string" > '1. Collections'< / span > < / span > < / strong > : [< a href = "#list" > List< / a > , < a href = "#dictionary" > Dict< / a > , < a href = "#set" > Set< / a > , < a href = "#tuple" > Tuple< / a > , < a href = "# range" > Range< / a > , < a href = "#enumerate" > Enumerate< / a > , < a href = "#iterator" > Iterator< / a > , < a href = "#generator" > Generator< / a > ],
< strong > < span class = "hljs-string" > < span class = "hljs-string" > '2. Types'< / span > < / span > < / strong > : [< a href = "#type" > Type< / a > , < a href = "#string" > String< / a > , < a href = "#regex" > Regex< / a > , < a href = "#format" > Format< / a > , < a href = "#numbers" > Numbers< / a > , < a href = "#combinatorics" > Combinatorics< / a > , < a href = "#datetime" > Datetime< / a > ],
< strong > < span class = "hljs-string" > < span class = "hljs-string" > '3. Syntax'< / span > < / span > < / strong > : [< a href = "#arguments" > Args< / a > , < a href = "#inline" > Inline< / a > , < a href = "#closure" > Closure< / a > , < a href = "#decorator" > Decorator< / a > , < a href = "#class" > Class< / a > , < a href = "#ducktypes" > Duck_Types< / a > , < a href = "#enum" > Enum< / a > , < a href = "#exceptions" > Exceptions< / a > ],
< strong > < span class = "hljs-string" > < span class = "hljs-string" > '4. System'< / span > < / span > < / strong > : [< a href = "#print" > Print< / a > , < a href = "#input" > Input< / a > , < a href = "#commandlinearguments" > Command_Line_Arguments< / a > , < a href = "#open" > Open< / a > , < a href = "#path" > Path< / a > , < a href = "#commandexecution" > Command_Execution< / a > ],
@ -237,7 +237,8 @@ flatter_list = list(itertools.chain.from_iterable(<list>))
product_of_elems = functools.reduce(< span class = "hljs-keyword" > lambda< / span > out, x: out * x, < collection> )
list_of_chars = list(< str> )
< / code > < / pre >
< pre > < code class = "python language-python hljs" > index = < list> .index(< el> ) < span class = "hljs-comment" > # Returns first index of item or raises ValueError.< / span >
< pre > < code class = "python language-python hljs" > < bool> = < el> < span class = "hljs-keyword" > in< / span > < collection> < span class = "hljs-comment" > # For dictionary it checks if key exists.< / span >
index = < list> .index(< el> ) < span class = "hljs-comment" > # Returns index of first occurrence or raises ValueError.< / span >
< list> .insert(index, < el> ) < span class = "hljs-comment" > # Inserts item at index and moves the rest to the right.< / span >
< el> = < list> .pop([index]) < span class = "hljs-comment" > # Removes and returns item at index or from the end.< / span >
< list> .remove(< el> ) < span class = "hljs-comment" > # Removes first occurrence of item or raises ValueError.< / span >
@ -285,27 +286,21 @@ Counter({<span class="hljs-string">'blue'</span>: <span class="hljs-number">3</s
< pre > < code class = "python language-python hljs" > < set> .remove(< el> ) < span class = "hljs-comment" > # Raises KeyError.< / span >
< set> .discard(< el> ) < span class = "hljs-comment" > # Doesn't raise an error.< / span >
< / code > < / pre >
< h3 id = "frozenset" > Frozenset< / h3 >
< h4 id = "ishashablemeaningitcanbeusedasakeyinadictionaryorasanelementinaset" > Is hashable, meaning it can be used as a key in a dictionary or as an element in a set.< / h4 >
< h3 id = "frozenset" > Frozen Set< / h3 >
< ul >
< li > < strong > Is immutable and hashable.< / strong > < / li >
< li > < strong > That means it can be used as a key in a dictionary or as an element in a set.< / strong > < / li >
< / ul >
< pre > < code class = "python language-python hljs" > < frozenset> = frozenset(< collection> )
< / code > < / pre >
< h2 id = "range" > < a href = "#range" name = "range" > #< / a > Range< / h2 >
< pre > < code class = "python language-python hljs" > < range> = range(to_exclusive)
< range> = range(from_inclusive, to_exclusive)
< range> = range(from_inclusive, to_exclusive, ±step_size)
< / code > < / pre >
< pre > < code class = "python language-python hljs" > from_inclusive = < range> .start
to_exclusive = < range> .stop
< / code > < / pre >
< h2 id = "enumerate" > < a href = "#enumerate" name = "enumerate" > #< / a > Enumerate< / h2 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-keyword" > for< / span > i, el < span class = "hljs-keyword" > in< / span > enumerate(< collection> [, i_start]):
...
< h2 id = "tuple" > < a href = "#tuple" name = "tuple" > #< / a > Tuple< / h2 >
< p > < strong > Tuple is an immutable and hashable list.< / strong > < / p >
< pre > < code class = "python language-python hljs" > < tuple> = ()
< tuple> = (< el> , )
< tuple> = (< el_1> , < el_2> , ...)
< / code > < / pre >
< h2 id = "namedtuple" > < a href = "#namedtuple" name = "namedtuple" > #< / a > Named Tuple< / h2 >
< ul >
< li > < strong > Tuple is an immutable and hashable list.< / strong > < / li >
< li > < strong > Named tuple is its subclass with named elements.< / strong > < / li >
< / ul >
< h3 id = "namedtuple" > Named Tuple< / h3 >
< p > < strong > Tuple's subclass with named elements.< / strong > < / p >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > collections < span class = "hljs-keyword" > import< / span > namedtuple
< span class = "hljs-meta" > > > > < / span > Point = namedtuple(< span class = "hljs-string" > 'Point'< / span > , < span class = "hljs-string" > 'x y'< / span > )
< span class = "hljs-meta" > > > > < / span > p = Point(< span class = "hljs-number" > 1< / span > , y=< span class = "hljs-number" > 2< / span > )
@ -319,6 +314,18 @@ Point(x=<span class="hljs-number">1</span>, y=<span class="hljs-number">2</span>
< span class = "hljs-meta" > > > > < / span > p._fields < span class = "hljs-comment" > # Or: Point._fields< / span >
(< span class = "hljs-string" > 'x'< / span > , < span class = "hljs-string" > 'y'< / span > )
< / code > < / pre >
< h2 id = "range" > < a href = "#range" name = "range" > #< / a > Range< / h2 >
< pre > < code class = "python language-python hljs" > < range> = range(to_exclusive)
< range> = range(from_inclusive, to_exclusive)
< range> = range(from_inclusive, to_exclusive, ±step_size)
< / code > < / pre >
< pre > < code class = "python language-python hljs" > from_inclusive = < range> .start
to_exclusive = < range> .stop
< / code > < / pre >
< h2 id = "enumerate" > < a href = "#enumerate" name = "enumerate" > #< / a > Enumerate< / h2 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-keyword" > for< / span > i, el < span class = "hljs-keyword" > in< / span > enumerate(< collection> [, i_start]):
...
< / code > < / pre >
< h2 id = "iterator" > < a href = "#iterator" name = "iterator" > #< / a > Iterator< / h2 >
< pre > < code class = "python language-python hljs" > < iter> = iter(< collection> ) < span class = "hljs-comment" > # Calling `iter(< iter> )` returns unmodified iterator.< / span >
< iter> = iter(< function> , to_exclusive) < span class = "hljs-comment" > # Sequence of return values until 'to_exclusive'.< / span >
@ -366,14 +373,31 @@ Point(x=<span class="hljs-number">1</span>, y=<span class="hljs-number">2</span>
< / code > < / pre >
< h3 id = "abc" > ABC< / h3 >
< p > < strong > An abstract base class introduces virtual subclasses, that don’t inherit from it but are still recognized by isinstance() and issubclass().< / strong > < / p >
< pre > < code class = "python language-python hljs" > < span class = "hljs-keyword" > from< / span > numbers < span class = "hljs-keyword" > import< / span > Integral, Rational, Real, Complex, Number
< span class = "hljs-keyword" > from< / span > collections.abc < span class = "hljs-keyword" > import< / span > Sequence, Collection, Iterable
< / code > < / pre >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > isinstance(< span class = "hljs-number" > 123< / span > , Number)
< span class = "hljs-keyword" > True< / span >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > collections.abc < span class = "hljs-keyword" > import< / span > Sequence, Collection, Iterable
< span class = "hljs-meta" > > > > < / span > isinstance([< span class = "hljs-number" > 1< / span > , < span class = "hljs-number" > 2< / span > , < span class = "hljs-number" > 3< / span > ], Iterable)
< span class = "hljs-keyword" > True< / span >
< / code > < / pre >
< pre > < code class = "text language-text" > ┏━━━━━━━━━━━━━━━━━━┯━━━━━━━━━━┯━━━━━━━━━━━━┯━━━━━━━━━━┓
┃ │ Sequence │ Collection │ Iterable ┃
┠──────────────────┼──────────┼────────────┼──────────┨
┃ list, range, str │ ✓ │ ✓ │ ✓ ┃
┃ dict, set │ │ ✓ │ ✓ ┃
┃ iter │ │ │ ✓ ┃
┗━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━┷━━━━━━━━━━━━┷━━━━━━━━━━┛
< / code > < / pre >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > numbers < span class = "hljs-keyword" > import< / span > Integral, Rational, Real, Complex, Number
< span class = "hljs-meta" > > > > < / span > isinstance(< span class = "hljs-number" > 123< / span > , Number)
< span class = "hljs-keyword" > True< / span >
< / code > < / pre >
< pre > < code class = "text language-text" > ┏━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━━┯━━━━━━━━━━┯━━━━━━┯━━━━━━━━━┯━━━━━━━━┓
┃ │ Integral │ Rational │ Real │ Complex │ Number ┃
┠────────────────────┼──────────┼──────────┼──────┼─────────┼────────┨
┃ int │ ✓ │ ✓ │ ✓ │ ✓ │ ✓ ┃
┃ fractions.Fraction │ │ ✓ │ ✓ │ ✓ │ ✓ ┃
┃ float │ │ │ ✓ │ ✓ │ ✓ ┃
┃ complex │ │ │ │ ✓ │ ✓ ┃
┗━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━┷━━━━━━━━━━┷━━━━━━┷━━━━━━━━━┷━━━━━━━━┛
< / code > < / pre >
< h2 id = "string" > < a href = "#string" name = "string" > #< / a > String< / h2 >
< pre > < code class = "python language-python hljs" > < str> = < str> .strip() < span class = "hljs-comment" > # Strips all whitespace characters from both ends.< / span >
< str> = < str> .strip(< span class = "hljs-string" > '< chars> '< / span > ) < span class = "hljs-comment" > # Strips all passed characters from both ends.< / span >
@ -481,16 +505,16 @@ Point(x=<span class="hljs-number">1</span>, y=<span class="hljs-number">2</span>
{< span class = "hljs-number" > 90< / span > :b} < span class = "hljs-comment" > # '1011010'< / span >
< / code > < / pre >
< h2 id = "numbers" > < a href = "#numbers" name = "numbers" > #< / a > Numbers< / h2 >
< pre > < code class = "python language-python hljs" > < int> = int(< float/str/bool> ) < span class = "hljs-comment" > # Or: math.floor(< float> )< / span >
< float> = float(< int/str/bool> )
< complex> = complex(real=< span class = "hljs-number" > 0< / span > , imag=< span class = "hljs-number" > 0< / span > ) < span class = "hljs-comment" > # Or: < real> + < real> j< / span >
< Fraction> = fractions.Fraction(numerator=< span class = "hljs-number" > 0< / span > , denominator=< span class = "hljs-number" > 1< / span > )
< / code > < / pre >
< ul >
< li > < strong > Int, float and complex are the only number types.< / strong > < / li >
< li > < strong > I use < code class = "python hljs" > < num> < / code > to mean any of the above and < code class = "python hljs" > < real> < / code > for either int or float.< / strong > < / li >
< li > < strong > < code class = "python hljs" > < span class = "hljs-string" > 'int(< str> )'< / span > < / code > and < code class = "python hljs" > < span class = "hljs-string" > 'float(< str> )'< / span > < / code > raise ValueError on malformed strings.< / strong > < / li >
< / ul >
< pre > < code class = "python language-python hljs" > < int> = int(< float/str/bool> ) < span class = "hljs-comment" > # Or: math.floor(< float> )< / span >
< float> = float(< int/str/bool> )
< complex> = complex(real=< span class = "hljs-number" > 0< / span > , imag=< span class = "hljs-number" > 0< / span > ) < span class = "hljs-comment" > # Or: < real> + < real> j< / span >
< / code > < / pre >
< h3 id = "basicfunctions" > Basic Functions< / h3 >
< pre > < code class = "python language-python hljs" > < num> = pow(< num> , < num> ) < span class = "hljs-comment" > # Or: < num> ** < num> < / span >
< pre > < code class = "python language-python hljs" > < num> = pow(< num> , < num> ) < span class = "hljs-comment" > # Or: < num> ** < num> < / span >
< real> = abs(< num> )
< int> = round(< real> )
< real> = round(< real> , ±ndigits)
@ -965,6 +989,25 @@ creature = Creature(Point(<span class="hljs-number">0</span>, <span class="hljs
< span class = "hljs-keyword" > for< / span > el < span class = "hljs-keyword" > in< / span > self.a:
< span class = "hljs-keyword" > yield< / span > el
< / code > < / pre >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > collections.abc < span class = "hljs-keyword" > import< / span > Sequence, Collection, Iterable
< span class = "hljs-meta" > > > > < / span > a = MyCollection([< span class = "hljs-number" > 1< / span > , < span class = "hljs-number" > 2< / span > , < span class = "hljs-number" > 3< / span > ])
< span class = "hljs-meta" > > > > < / span > isinstance(a, Sequence), isinstance(a, Collection), isinstance(a, Iterable)
(< span class = "hljs-keyword" > False< / span > , < span class = "hljs-keyword" > True< / span > , < span class = "hljs-keyword" > True< / span > )
< / code > < / pre >
< h3 id = "iterator-1" > Iterator< / h3 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-class" > < span class = "hljs-keyword" > class< / span > < span class = "hljs-title" > Counter< / span > :< / span >
< span class = "hljs-function" > < span class = "hljs-keyword" > def< / span > < span class = "hljs-title" > __init__< / span > < span class = "hljs-params" > (self)< / span > :< / span >
self.i = < span class = "hljs-number" > 0< / span >
< span class = "hljs-function" > < span class = "hljs-keyword" > def< / span > < span class = "hljs-title" > __next__< / span > < span class = "hljs-params" > (self)< / span > :< / span >
self.i += < span class = "hljs-number" > 1< / span >
< span class = "hljs-keyword" > return< / span > self.i
< span class = "hljs-function" > < span class = "hljs-keyword" > def< / span > < span class = "hljs-title" > __iter__< / span > < span class = "hljs-params" > (self)< / span > :< / span >
< span class = "hljs-keyword" > return< / span > self
< / code > < / pre >
< pre > < code class = "python language-python hljs" > < span class = "hljs-meta" > > > > < / span > counter = Counter()
< span class = "hljs-meta" > > > > < / span > next(counter), next(counter), next(counter)
(< span class = "hljs-number" > 1< / span > , < span class = "hljs-number" > 2< / span > , < span class = "hljs-number" > 3< / span > )
< / code > < / pre >
< h3 id = "callable" > Callable< / h3 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-class" > < span class = "hljs-keyword" > class< / span > < span class = "hljs-title" > Counter< / span > :< / span >
< span class = "hljs-function" > < span class = "hljs-keyword" > def< / span > < span class = "hljs-title" > __init__< / span > < span class = "hljs-params" > (self)< / span > :< / span >
@ -1572,29 +1615,18 @@ logger.<level>(<span class="hljs-string">'A logging message.'</span>)
< li > < strong > < code class = "python hljs" > < span class = "hljs-string" > '< str> '< / span > < / code > - Max age as a string: < code class = "python hljs" > < span class = "hljs-string" > '1 week, 3 days'< / span > < / code > , < code class = "python hljs" > < span class = "hljs-string" > '2 months'< / span > < / code > , …< / strong > < / li >
< / ul >
< h2 id = "scraping" > < a href = "#scraping" name = "scraping" > #< / a > Scraping< / h2 >
< h4 id = "scrapesandprintspythonsurlandversionnumberfromwikipedia" > Scrapes and prints Python's URL and version number from Wikipedia:< / h4 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-comment" > # $ pip3 install requests beautifulsoup4< / span >
< span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > import< / span > requests
< span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > bs4 < span class = "hljs-keyword" > import< / span > BeautifulSoup
< span class = "hljs-meta" > > > > < / span > url = < span class = "hljs-string" > 'https://en.wikipedia.org/wiki/Python_(programming_language)'< / span >
< span class = "hljs-meta" > > > > < / span > page = requests.get(url)
< span class = "hljs-meta" > > > > < / span > doc = BeautifulSoup(page.text, < span class = "hljs-string" > 'html.parser'< / span > )
< span class = "hljs-meta" > > > > < / span > table = doc.find(< span class = "hljs-string" > 'table'< / span > , class_=< span class = "hljs-string" > 'infobox vevent'< / span > )
< span class = "hljs-meta" > > > > < / span > rows = table.find_all(< span class = "hljs-string" > 'tr'< / span > )
< span class = "hljs-meta" > > > > < / span > link = rows[< span class = "hljs-number" > 11< / span > ].find(< span class = "hljs-string" > 'a'< / span > )[< span class = "hljs-string" > 'href'< / span > ]
< span class = "hljs-meta" > > > > < / span > ver = rows[< span class = "hljs-number" > 6< / span > ].find(< span class = "hljs-string" > 'div'< / span > ).text.split()[< span class = "hljs-number" > 0< / span > ]
< span class = "hljs-meta" > > > > < / span > link, ver
(< span class = "hljs-string" > 'https://www.python.org/'< / span > , < span class = "hljs-string" > '3.7.2'< / span > )
< / code > < / pre >
< h3 id = "selenium" > Selenium< / h3 >
< p > < strong > Library for scraping dynamically generated web content.< / strong > < / p >
< pre > < code class = "python language-python hljs" > < span class = "hljs-comment" > # $ brew cask install chromedriver< / span >
< span class = "hljs-comment" > # $ pip3 install selenium< / span >
< span class = "hljs-meta" > > > > < / span > < span class = "hljs-keyword" > from< / span > selenium < span class = "hljs-keyword" > import< / span > webdriver
< span class = "hljs-meta" > > > > < / span > driver = webdriver.Chrome()
< span class = "hljs-meta" > > > > < / span > driver.get(url)
< span class = "hljs-meta" > > > > < / span > xpath = < span class = "hljs-string" > '//*[@id="mw-content-text"]/div/table[1]/tbody/tr[7]/td/div'< / span >
< span class = "hljs-meta" > > > > < / span > driver.find_element_by_xpath(xpath).text.split()[< span class = "hljs-number" > 0< / span > ]
< span class = "hljs-string" > '3.7.2'< / span >
< span class = "hljs-keyword" > import< / span > requests
< span class = "hljs-keyword" > from< / span > bs4 < span class = "hljs-keyword" > import< / span > BeautifulSoup
url = < span class = "hljs-string" > 'https://en.wikipedia.org/wiki/Python_(programming_language)'< / span >
page = requests.get(url)
doc = BeautifulSoup(page.text, < span class = "hljs-string" > 'html.parser'< / span > )
table = doc.find(< span class = "hljs-string" > 'table'< / span > , class_=< span class = "hljs-string" > 'infobox vevent'< / span > )
rows = table.find_all(< span class = "hljs-string" > 'tr'< / span > )
link = rows[< span class = "hljs-number" > 11< / span > ].find(< span class = "hljs-string" > 'a'< / span > )[< span class = "hljs-string" > 'href'< / span > ]
ver = rows[< span class = "hljs-number" > 6< / span > ].find(< span class = "hljs-string" > 'div'< / span > ).text.split()[< span class = "hljs-number" > 0< / span > ]
print(link, ver)
< / code > < / pre >
< h2 id = "web" > < a href = "#web" name = "web" > #< / a > Web< / h2 >
< pre > < code class = "python language-python hljs" > < span class = "hljs-comment" > # $ pip3 install bottle< / span >
@ -1677,7 +1709,7 @@ Line # Hits Time Per Hit % Time Line Contents
time_str = datetime.now().strftime(< span class = "hljs-string" > '%Y%m%d%H%M%S'< / span > )
filename = < span class = "hljs-string" > f'profile-< span class = "hljs-subst" > {time_str}< / span > .png'< / span >
drawer = output.GraphvizOutput(output_file=filename)
< span class = "hljs-keyword" > with< / span > PyCallGraph(output= drawer):
< span class = "hljs-keyword" > with< / span > PyCallGraph(drawer):
< code_to_be_profiled>
< / code > < / pre >
< h2 id = "numpy" > < a href = "#numpy" name = "numpy" > #< / a > NumPy< / h2 >
Jure Šorn
6 years ago