Sunday, June 8, 2014
On 9:12 PM by Unknown No comments
Here's a syntax cheatsheet for python programmers!
Yes, we know how you love cheat sheets, and for a complex language like python, cheatsheets are a big boon! So to add to your collection, here we bring to you a cheat sheet with list of syntax used in python. Happy coding!
Courtesy: Himanshu Teotia
Language Category: Object Oriented, Dynamically typed, Has anonymous functions | |
Various | |
indentation | block (grouping statements, especially when statements are not expressions) |
\ | breaking lines (useful when end-of-line and/or indentation has a special meaning) |
# | commenting (until end of line) |
< > <= >= | comparison |
min / max | comparison (min / max (binary or more)) |
cmp | comparison (returns 3 values (i.e. inferior, equal or superior)) |
class X: """... """ def x(): """... """ | documentation comment |
Err:510 | equality / inequality (deep) |
Err:510 | equality / inequality (deep) |
is / is not | equality / inequality (shallow) |
gc.collect() | force garbage collection |
( ... ) | grouping expressions |
__file__ | information about the current line and file |
eval | runtime evaluation |
exec | runtime evaluation |
case-sensitive | tokens (case-sensitivity (keywords, variable identifiers...)) |
[_a-zA-Z][_a-zA-Z0-9]* | tokens (variable identifier regexp) |
CamelCase for classes, underscores for methods | tokens (what is the standard way for scrunching together multiple words) |
= | variable assignment or declaration (both) |
global v1, v2 | variable assignment or declaration (declaration) |
Functions | |
functools.partial(f, a) | partial application (in the examples below, a normal call is "f(a,b)") (give the first argument) |
lambda a, b: ... | anonymous function |
f(a,b,...) | function call |
f() | function call (with no parameter) |
__getattr__ | function called when a function is not defined (in dynamic languages) |
def f(para1, para2, ...): ... | function definition |
return | function return value (breaks the control flow) |
inspect.stack()[1] | runtime inspecting the caller information |
Control Flow | |
continue / break | breaking control flow (continue / break) |
return | breaking control flow (returning a value) |
try: a except exn: ... | exception (catching) |
finally | exception (cleanup: code executed before leaving) |
raise | exception (throwing) |
if c: ... | if_then |
b1 if c else b2 | if_then_else |
if c: b1 elif c2: b2 else: b3 | if_then_else |
for i in xrange(10, 0, -1) | loop (for each value in a numeric range, 1 decrement) |
for i in xrange(1, 11) | loop (for each value in a numeric range, 1 increment (see also the entries about ranges)) |
for i in xrange(1, 11, 2) | loop (for each value in a numeric range, free increment) |
while c: ... | loop (while condition do something) |
; | sequence |
end-of-line | sequence |
Types | |
t(e) | cast (computed conversion (calls an internal or a user-defined function)) |
n = t | declaration |
Object Oriented & Reflexivity | |
super(Class, self).meth(args) | accessing parent method |
class | class declaration |
first parameter | current instance |
__class__ | get the type/class corresponding to an object/instance/value |
hasattr(obj, "meth") | has the method |
class child(parent): | inheritance |
del, __del__ | manually call an object's destructor |
object.method(para) | method invocation |
object.method() | method invocation (with no parameter) |
dir | methods available |
copy.copy(o) | object cloning |
class_name(...) | object creation |
isinstance | testing class membership |
Package, Module | |
automatically done based on the file name | declare |
__all__ = [ ... ] | declare (selective export) |
from p import * | import (everything into current namespace) |
import p | import (package (ie. load the package)) |
from p import name1, name2, ... | import (selectively) |
0 | package scope |
Strings | |
s[n] | accessing n-th character |
chr | ascii to character |
ord | character to ascii |
str, `e`, repr | convert something to a string (see also string interpolation) |
* | duplicate n times |
s[n:m+1] | extract a substring |
index | locate a substring |
find | locate a substring |
rindex | locate a substring (starting at the end) |
rfind | locate a substring (starting at the end) |
'''...''', """...""" | multi-line |
pickle.dump | serialize (marshalling) |
simple print (on any objects) | |
print e, | simple print (on any objects) |
% | sprintf-like |
0 | string concatenation |
Err:510 | string equality & inequality |
Err:510 | string equality & inequality |
len | string size |
"\n" | strings (end-of-line (without writing the real CR or LF character)) |
"... %(v)s ..." % vars() | strings (with interpolation of variables) |
'...' | strings (with no interpolation of variables) |
"..." | strings (with no interpolation of variables) |
'''...''' | strings (with no interpolation of variables) |
"""...""" | strings (with no interpolation of variables) |
str | type name |
pickle.load | unserialize (un-marshalling) |
upper / lower | upper / lower case character |
upper / lower / capitalize | uppercase / lowercase / capitalized string |
Booleans | |
False | false value |
None | false value |
0 | false value |
"" | false value |
() | false value |
[] | false value |
{} | false value |
not | logical not |
or / and | logical or / and (short circuit) |
True | true value |
anything not false | true value |
bool | type name |
Bags and Lists | |
zip(*l) | 2 lists from a list of couples |
a.insert(i, e) | adding an element at index (side-effect) |
append | adding an element at the end (side-effect) |
l[1:] | all but the first element |
reduce | f(... f(f(init, e1), e2) ..., en) |
index | find an element |
for v in l: ... | for each element do something |
pop | get the last element and remove it |
in | is an element in the list |
any | is the predicate true for an element |
all | is the predicate true for every element |
enumerate(l) | iterate with index |
s.join(l) | join a list of strings in a string using a glue string |
filter | keep elements (matching) |
[ x for x in l if p(x) ] | keep elements (matching) |
a[-1] | last element |
0 | list concatenation |
[ a, b, c ] | list constructor |
zip | list of couples from 2 lists |
list | list out of a bag |
len | list size |
a[i] | list/array indexing |
set | remove duplicates |
reverse | reverse |
reversed | reverse |
l[::-1] | reverse |
min / max | smallest / biggest element |
sort | sort |
sorted | sort |
map | transform a list (or bag) in another one |
[ f(x) for x in l ] | transform a list (or bag) in another one |
map | transform two lists in parallel |
list | type name |
Various Data Types | |
a, | computable tuple (these are a kind of immutable lists playing a special role in parameter passing) (1-uple) |
tuple([a]) | computable tuple (these are a kind of immutable lists playing a special role in parameter passing) (1-uple) |
() | computable tuple (these are a kind of immutable lists playing a special role in parameter passing) (empty tuple) |
*t | computable tuple (these are a kind of immutable lists playing a special role in parameter passing) (using a tuple for a function call) |
h.get(k, returned_value_when_k_unfound) | dictionary (access: read) |
h[k] | dictionary (access: read/write) |
{ a: b, c: d } | dictionary (constructor) |
has_key | dictionary (has the key ?) |
k in h | dictionary (has the key ?) |
k not in h | dictionary (has the key ?) |
keys | dictionary (list of keys) |
values | dictionary (list of values) |
update | dictionary (merge) |
del h[k] | dictionary (remove by key) |
dict | dictionary (type name) |
or | optional value (null coalescing) |
None | optional value (null value) |
v | optional value (value) |
range | range (inclusive .. exclusive) |
0 | record (selector) |
a, b, c | tuple constructor |
tuple | tuple type |
Mathematics | |
+ / - / * / / | addition / subtraction / multiplication / division |
& / | / ^ | bitwise operators (and / or / xor) |
~ | bitwise operators (bitwise inversion) |
<< / >> | bitwise operators (left shift / right shift / unsigned right shift) |
divmod | euclidian division (both quotient and modulo) |
** | exponentiation (power) |
pow | exponentiation (power) |
log10 | logarithm (base 10) |
log(val, 2) | logarithm (base 2) |
log | logarithm (base e) |
% | modulo (modulo of -3 / 2 is 1) |
-0 | negation |
1000., 1E3 | numbers syntax (floating point) |
07, 0xf | numbers syntax (integers in base 2, octal and hexadecimal) |
1000 | numbers syntax (integers) |
mathematical | operator priorities and associativities (addition vs multiplication) |
mathematical | operator priorities and associativities (exponentiation vs negation (is -3^2 equal to 9 or -9)) |
random | random (random number) |
random.seed | random (seed the pseudo random generator) |
sqrt / exp / abs | square root / e-exponential / absolute value |
sin / cos / tan | trigonometry (basic) |
asin / acos / atan | trigonometry (inverse) |
int / round / floor / ceil | truncate / round / floor / ceil |
float, decimal.Decimal | type name (floating point) |
int, long | type name (integers) |
Threads | |
OtherThread.join() | Joining Another Thread (Suspending a thread until another thread completes) |
class class_name(threading.Thread) {[override run method] } | thread definition |
Courtesy: Himanshu Teotia
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