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Python Facts
Python2 is backward compatible; whereas Python3 is backward
INCOMPATIBLE.
Python supports OOPs concepts. But, in python, both private
and protected modes are having same authority. This is the
only limitation in python becoming complete OOP language.
Python interpreter generates byte-code, so the python
applications are platform-independent.
Python runs faster than java, but slower than C language.
Python was written in C language.
Pre/Post increment/decrement like x++,x--,--x,++x, are
INVALID
in python
Compound operations such as +=,-=,*=,/= are VALID in Python
Python is case-sensitive i.e., variable work is different
from variable Work, or WORK
Using underscores (eg:price_at_opening) and Camel-casing
(eg:PriceAtOpening)is VALID
Multiple Assignments are VALID in python.
Eg: x=y=z=1
Parallel assignment (or unpacking) is POSSIBLE in python
Eg: a,b=1,2
(x,y,z)=1,2,3
In python 2, Print is a statement. In python 3, print is a
function.
To use print() function of python 3 in python2, place this
statement in the first lines of script:
from __future__ import print_function
= assignment operator
== Operator to check value equivalence
is Operator to check identity of objects; looks at object
level
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in Operator to check identity of objects; looks at index
level
!= not-equal-to operator
not-equal-to operator. Available only in python2.
# comment operator in python; called as
octothorpe/pound/hash/mesh
>>> Input operator, shows readiness of interpreter.
Called as
chevron
^ bit-wise operator. Not power operator. Called as caret
; used to separate TWO or more statements in the same line.
or docstrings. Used for multiple-line
comment in python scripts. Differs from using #. Appears
in the output. Useful, especially, in modules.
#! Called shebang. Used as the first character in python
script.
\ line-continuation operator. Used when a statement spans
more than one line.
Eg: print Udhay\
Prakash
() used for tuples
[] used for lists
{} used for dictionaries
([]) used for sets
Switch-case condition is not defined in python. Instead, If-
elif-else ladder can be used. Also, dictionary of
functions can be used.
Eg:
>>> result={
... 'a':lambda x :x*5,
... 'b':lambda x:x+7,
... 'c':lambda x:x-2}
>>> result['b'](10)
17
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Indentation is both boon and bane (for beginners) for
python.
Use spaces instead of Tabs in scripts.
Eg:
>>> a=2
>>> a
2
>>> a=2
Traceback ( File "", line 1
a=2
^
IndentationError: unexpected indent
Running python with t option prints warning messages when
tabs and spaces are mixed inconsistently within the same
program block.
Running python with tt option turns these warning messages
in
to TabError exception.
raw_input() takes any input as string type.
input() takes any input type dynamically.
&&,|| are defined operators in python
and boolean operator for AND operation
or boolean operator for OR operation
not Boolean operator for NOT operation
set operators
| union operator for sets
& intersection operator for sets
- Set difference operator
Eg: c=t-s# set c contains items in set t, but not in set s
^ Symmetric difference operator for sets
Eg: d=t^s # set d contains items in set t or set s, but
not common items in both.
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bitwise Operators
& bit-wise AND operator
| bit-wise OR operator
^ bit-wise XOR operator
~ bit-wise invert operator. Eg: ~5 results in -6
Bit-wise invert of x is (x+1)
>> left shift operator
Eg: 15>>1
7
Explanation: 15-1111 (in 8421 convention)
15>>1 means shifting one position left.
It becomes 0111 i.e., 7
