Python

Print("Hello, World")

Assignment
=   gets
+=  plus gets (x += y is x = x + y)
-=  minus gets
*=  times gets
/=  quotient gets
%=  residue gets
**= power gets
//= floor-quotient gets

Logic
bool(x) True if x is true else False
not x   False if x else True
x or y  x if x else y
x and y y if x else x
any(x)  True if any item of x is true
all(x)  True if all items of x are true
==      equal
!=      not equal
<>      not equal
>       more
<       less
>=      more or equal
<=      less or equal

Arithmetic
int(x)       integer form of the string x
bin(x)       binary string form of the integer x
complex(x,y) complex number with real part x and imaginary part y; x + y * 1j
x+y          x plus y
x-y          x minus y
x*y          x times y
x/y          quotient of x divided by y
x%y          remainder of x divided by y; x mod y; (divisor's sign: 3 % -6 == 
-3)
x**y         x to the power of y
x//y         integer quotient of x divided by y
abs(x)       absolute value of x
divmod(x,y)  (x // y , x % y)
pow(x,y,z)   (x**y)%z
max(x)       maximum item of x
min(x)       minimum item of x
x+=y         x plus gets y; x = x + y
-=           minus gets
*=           times gets
/=           quotient gets
%=           residue gets
**=          power gets
//=          floor-quotient gets
==           equal
!=           not equal
<>           not equal
>            more
<            less
>=           more or equal
<=           less or equal

Lists

len(x)        length of x
x.append(y)   insert y after the last item of x
x.extend(y)   join the list y to the end of the list x
x.insert(y,z) insert z before the item of x with index y
x.remove(y)   remove first occurrence of y in x
x.pop()       return then remove the last item of x
x.pop(y)      return then remove the item of x with index y
x.index(y)    give index of first occurrence of y in x (error otherwise)
x.count(y)    give count of occurrences of y in x
x.sort()      sort x in increasing order
x.reverse()   reverse the order of items of x

Sets
x.add(y)                   put y in x
x.remove(y)                take y from x give KeyError if y is not in x
x.discard(y)               take y from x
x.pop()                    return an item from x, remove it, and give KeyError 
if x empty
len(x)                             cardinality of set x
x in y                             is x in y?
x not in y                         is x not in y?
x.issubset(y)              x <= y  is x a subset of y?
x.issuperset(y)            x >= y  is x a superset of y?
x.union(y)                 x |  y  give union of x and y
x.intersection(y)          x &  y  give intersection of x and y
x.difference(y)            x -  y  give complement of y in x
x.symmetric_difference(y)  x ^  y  give symmetric difference of x and y
x.update(y)                x |= y  x gets x|y
x.intersection_update(y)   x &= y  x gets x&y
x.difference_update(y)     x -= y  x gets x-y
x.symmetric_difference_update(y)  x ^= y  x gets x^y

Strings
'abc'    give string 'abc'
"abc"    give string 'abc'
'"'      give string '"'
"'"      give string "'"

'\''     give string "'"
"\""     give string '"'
'''
a
b
c'''     give string '\na\nb\nc'
"""
a
b
c"""     give string '\na\nb\nc'
'''
"""
'''      give string '\n"""\n'
"""
'''
"""      give string "\n'''\n"
'''\
a\
b\
c\
'''      give string 'abc'
"""\
a\
b\
c\
"""      give string 'abc'
'a' 'b'  give string 'ab'
"a" "b"  give string 'ab'
'a' "b"  give string 'ab'
r'...'  raw string i.e. escape characters are not interpreted
3*'c'   gives 'ccc'
len(x)        length of string x
x.isalnum()   are all characters in string x alphanumeric characters?
x.isalhpa()   are all characters in x alphabetic characters?
x.isdigit()   are characters of x digits only?
x.islower()   are alphabetic characters of x lowercase?
x.isupper()   are alphabetic characters of x uppercase?
x.ljust(y,z)  right justify x on line of width y padded by char z
x.center(y,z) center justify x on line of width y padded by char z
x.rjust(y,z)  left justify x on width y line, pad with char z
x.join(y)     join string items of y after inserting x between items of y

Control
x or y    x if x else y
x and y   y if x else x
for x in y:          perform f(x) for each x in y
    f(x)
if c:                cond c;t;f
    t
else:
    f
if c0:               cond c0 t0;
    t0                    c1 t1;
elseif c1:                 1  d
    t1
else:
    d
for x in y:          this will run forever
    y.insert(0,x)
for x in y[:]:       this will not run forever, x iterates over y[:] rather 
than y
    y.insert(0,x)

Idioms
x[1:]==x[:-1]   True if all items of x are the same

Built-In Functions
abs(x)        give the classical norm of x
all(x)        give True if each item of x is true
any(x)        give True if any item of x is true
ascii()
bin(x)        give binary (string) form of int x
bool(x)       give True if x is true else give False
bytearray() 
bytes()
callable()
chr(x)        give string for Unicode character at x
classmethod()
compile()
complex(x,y)  give x + y * 1j
delattr()
dict()
dir()
divmod()
enumerate()
eval()
exec()
filter()
float()
format()
frozenset()
getattr()
globals()
hasattr()
hash()
help()
hex()
id()
input()
int()
isinstance()
issubclass()
iter()
len()
list()
locals()
map()
max()
memoryview()
min()
next()
object()
oct()
open()
ord()
pow()
print()
property()
range()
repr()
reversed()
round()
set()
setattr()
slice()
sorted()
staticmethod()
str()
sum()
super()
tuple()
type()
vars()
zip()
__import__()

Implementations of k Functions
import itertools
def where(x):
 return itertools.chain.from_iterable([[i]*j for i,j in enumerate(x)])
def where(x):
 return [i for i in range(len(x)) for _ in range(x[i])]
def drop(x,y):
 return y[x:]
def take(x,y):
 return [y[i] for i in x]

import cmath
cmath.phase(x)   gives the phase or argument of the complex number x
abs(x)           gives the absolute value of the complex number x
cmath.polar(x)   gives polar representation of complex x i.e. 
(abs(x),cmath.phase(x))
cmath.rect(x,y)  rect from polar: x * (math.cos(y) + math.sin(y)*1j)

from collections import Counter
Counter(x)        count items of x using a map(dict)
x.elements()      give iterator of elements y of counter x each repeated x[y] 
times
x.most_common()   give list of (item, count) ordered by count (equals listed 
arbitrarily)
x.most_common(y)  give first y items of x.most_common()
x.subtract(y)     subtract item's count in y from item's count in x
x.update(y)       add count of items in a Counter y, or Counter(y) if y is list 
etc.

import calendar
calendar.weekday(y,m,d) give index of day of week on ymd with 0 = Monday
calendar.day_name       array of name of day of week in current local 0=Monday

import time
time.strptime(x)   change x from "%a %b %d %H:%M:%S %Y" to time.struct_time 
form (tuple)
time.strptime(x,y) change string x from format string y to time.struct_time
time.mktime(x)     change struct_time x into the (float) number of seconds 
since epoch

import textwrap
textwrap.wrap(x,y) give lines of string x with width y
textwrap.fill(x,y) gives string of lines of string x with width y

from datetime import datetime
x=datetime.strptime(y,z) x gets datetime object from string y formatted by z
time.struct_time # https://docs.python.org/3/library/time.html#time.struct_time
Time String Format Codes 
(https://docs.python.org/3/library/time.html#time.strftime)
%a Locale’s abbreviated weekday name.  
%A Locale’s full weekday name.  
%b Locale’s abbreviated month name.  
%B Locale’s full month name.  
%c Locale’s appropriate date and time representation.  
%d Day of the month as a decimal number [01,31].  
%H Hour (24-hour clock) as a decimal number [00,23].  
%I Hour (12-hour clock) as a decimal number [01,12].  
%j Day of the year as a decimal number [001,366].  
%m Month as a decimal number [01,12].  
%M Minute as a decimal number [00,59].  
%p Locale’s equivalent of either AM or PM.
%S Second as a decimal number [00,61].
%U Week number of the year (Sunday as the first day of the week) as a decimal 
number [00,53]. All days in a new year preceding the first Sunday are 
considered to be in week 0.
%w Weekday as a decimal number [0(Sunday),6].  
%W Week number of the year (Monday as the first day of the week) as a decimal 
number [00,53]. All days in a new year preceding the first Monday are 
considered to be in week 0.
%x Locale’s appropriate date representation.  
%X Locale’s appropriate time representation.  
%y Year without century as a decimal number [00,99].  
%Y Year with century as a decimal number.  
%z Time zone offset indicating a positive or negative time difference from 
UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and 
M represents decimal minute digits [-23:59, +23:59].  
%Z Time zone name (no characters if no time zone exists).  
%% A literal '%' character.



Sources
https://www.python.org/doc/