Sequences indexing
Base Types
Python 3 Basic Reference Card
©2012 - Laurent Pointal
Licence Creative Commons Attribution 2
Official Python docu mentation on
http://docs.python. org/py3k
0783 -192int
9.23 -1.7e-60.0float
True Falsebool
"One\nTwo" 'I\'m'str
"""X\tY\tZ
1\t2\t3"""
10-6
tab char
new line
multiline
Container Types
list [1,5,9] ["x",11,8.9] ["mot"] []
tuple (1,5,9) 11,"y",7.4 ("mot",) ()
dict
{1:"one",3:"three",2:"two",3.14:"π"}
{"key":"value"}
set
{}
{1,9,3,0}
◾ ordered sequence, fast index access, repeatable values
set()
◾ no a priori order, unique key, fast key access%; keys%= base types or tuples
{"key1","key2"}
unmodifiable
Variables assignment
x = 1.2+8+sin(0)
y,z,r = 9.2,-7.6,"bad"
value or calculation expression
variable name (identifier)
a‥zA‥Z_ followed by a‥zA‥Z_0‥9
◽ diacritics allowed but should be avoided
◽ language keywords forbidden
◽ min/MAJ case discrimination
expression with just comas
unmodifiable,
ordered sequence of chars
dictionnary
integer, float, boolean, string
container with several
values (here a tuple)
variables
names
Identifiers
☺ a toto x7 y_max BigOne
☹ 8y and
x+=3x-=2
increment
decrement
Conversions
for lists, tuples, char strings, …
int("15")
float("-11.24e8")
bool
str(78.3)repr("Text")
can specify integer number base in 2nd parameter
int(15.56)truncate decimal part (round(15.56) for rounded integer)
and for litteral representation
type(expression)
use comparators (with ==, !=, <, >, …), logial boolean result
see verso for string formating allowing finer control
":".join(['toto','12','pswd'])'toto:12:pswd'
joining string sequence of strings
"words with spaces".split() ['words','with','spaces']
"1,4,8,2".split(",")['1','4','8','2']
splitting string
dict([(3,"three"),(1,"one")]){1:'one',3:'three'}
list("abc")['a','b','c']
use each element
from sequence
set(["one","two"]){'one','two'}
use each element
from sequence
lst=[11, 67, "abc", 3.14, 42, 1968] lst[1]→67
lst[-2]→42
0 1 2 3 54
-6 -5 -
4
-3 -1-2
individual access to items via [index]
positive index
negative index
0 1 2 3 54 6
-6 -5 -4 -3 -1-2
negative slice
positive slice
access to sub-sequences via [start slice:end slice:step]
len(lst)6
lst[1:3]→[67,"abc"]
lst[::2]→[11,"abc",42]
lst[-3:-1]→[3.14,42]
lst[:3]→[11,67,"abc"]
lst[:-1]→[11,67,"abc",3.14,42]
lst[4:]→[42,1968]
lst[1:-1]→[67,"abc",3.14,42]
lst[:]→[11,67,"abc",3.14,42,1968]
missing slice indication → from start / up to end
Conditional Statement
if x==42:
# block if logical expression x==42 is true
print("real truth")
elif x>0:
# block else if logical expression x>0 is true
print("be positive")
elif bFinished:
# block else if boolean variable bFinished is true
print("how, finished")
else:
# block else for other cases
print("when it's not")
Boolean Logic Statements Blocks
parent statement:
statements block 1…
⁝
parent statement:
statements block 2…
⁝
next statement after block 1
indentation%!
Comparators: < > <= >= == !=
≠=≥≤
a and b
a or b
not a
logical and
logical or
logical not
one or other or both
twice simultaneously
if logical expression:
statements block
statements block executed
only if a condition is true
True
False
true constant value
false constant value
can go with several else if, else if... and only one final else,
example%:
lst[-1]→1968
lst[0]→11
last one
first one
x=None «%undefined%» constant value
Maths
Operators: + - * / // % **
× ÷
integer ÷ ÷ remain
abfrom math import sin,pi…
' escaped
abs(-3.2)→3.2
round(3.57,1)→3.6
☝ floating point numbers… approximated value!
sin(pi/4)→0.707…
cos(2*pi/3)→-0.4999…
sqrt(81)→9.0 √
log(e**2)→2.0
angles in radians
acos(0.5)→1.0471…
etc. (cf doc)
(1+5.3)*2→12.6
for variables, funct ions,
modules, classes… names
Mémento v1.0.5a
