NUMBERS:
- the answer for 0.1+0.2-0.3 should be zero , but the answer is5.551115123125783e-17
The reason behind this is Relative Error ,Ulps and Rounding according to “What Every Computer Scientist Should Know About Floating-Point Arithmetic“, by David Goldberg, published in the March, 1991.
python 3 perform true division . eg -output of 1/2 is 0.5
Rules for variable names :
- Names can not start with a number
- there are no spaces in variable name
- no special symbols can be used
- no special keywords can be used
python uses dynamic typing whereas C++ is static typing. Pros and Cons of dynamic typing:
- User friendly
- faster development time
- May cause confusion between unexpected data types
type() -returns the data type of variable
Strings:
strings are ordered sequences .It can be denoted as ‘hello’ or “I don’t have time”,in second example if we had used a single quote then it would have ended at n.
Indexing grab a single character from a string[]. Reverse indexing is also possible.
slicing we grab a sub section of multiple characters .[star:stop:step].
for eg :mystring="Programmer Prodigy"
then to index we can use mystring[location of character in the string],string starts from location 0.
if we use mystring[starting_location:ending_location(not including the ending location):step size] ,we could address that to a sub string.
mystring[::-1] : means reversing the string,for eg mystring[::-1]=ygidorp remmargorp
\n-> a new line ,\t->four spaces
Built in functions
- len()- counts the white spaces
- concatenation – is done with the help of a ‘+”sign
- split()=by default it splits the string bu white spaces . Could also be done on a character
String properties
- Immutability
name="Sam"
#name[0]='P' will not work, so we could use
previous=name[1:]
'P'+previous
Formatting
A way to format a string is with the string.format()method .Syntax is print('This is a string {}'.format('Inserted'))
for example :
print('The {} {} {} '.format('fox','brown','quick'))
o/p->The fox brown quick
if we want to order the formatting of the string
print('The {2} {1} {0} '.format('fox','brown','quick'))
or
print('The {q} {b} {f}' .format(f='fox',b='brown',q='quick'))
precision of the result:
"{value:width.precision f}"
for ex-
pi = 22/7
print("the value of pi {p:1.8f}".format(p=pi))
string literal method :
This method came into use from python 3.6.
for example:
name="Hridyesh"
print(f'Hello ,my name is {name}')
Programmer Prodigy 