Python 3

return the absolute value of a number

#!/usr/bin/python

print(abs(-10))
print(abs(-3.14))

return True if all elements of the iterable are true

#!/usr/bin/python

l = [not (i % 3) for i in range(1, 5)] # [False, False, True, False]
print(any(l)) # True
print(all(l)) # False

convert an integer number to a binary string prefixed with “0b”

#!/usr/bin/python

print(bin(9)) # convert int to bin

if the argument is false or omitted, this returns False; otherwise it returns True

#!/usr/bin/python

print(bool(0)) # False
print(bool()) # False
print(bool(1)) # True
print(bool(range(4))) # True

Converts a Unicode code point to a character, The valid range for the argument is from 0 through 1,114,111

Raise ValueError, if i is outside that range

#!/usr/bin/python
 
for i in range(256):
    print(chr(i))

without arguments, return the list of names in the current local scope, with an argument, attempt to return a list of valid attributes for that object

#!/usr/bin/python

print(dir())
print(dir(str))

quotient and remainder

#!/usr/bin/python

a = divmod(10, 3) # same as (a//b, a%b)
print(a) # (3, 1), quotient, remainder

d = divmod(3.5, 3) # (q, a%b)
print(d) # (1.0, 0.5)

return an enumerate object instead of a list of tuples

#!/usr/bin/python

for index, ele in enumerate(range(4)):
    print(index, ele)

r = enumerate(range(0, 40, 10))
print(list(r))

expression argument is parsed and evaluated as a Python expression

#!/usr/bin/python

x = 1
print(eval('1+x'))

return a floating number from a number or string

raise OverflowError, if the argument is outside the range of a Python float

#!/usr/bin/python

print(float("+3.14")) # 3.14
print(float("   -3.14")) # -3.14
print(float("3.14e+2")) # 314.0
print(float("3.14e-2")) # 0.0314
print(float("Inf")) # inf

invoke the built-in help system, is intended for interactive use

help() # switch to interactive help environment, Ctrl+C to quit
help(str) # get the help documentation of str class

convert an integer number to a lowercase hexadecimal string prefixed with “0x”

#!/usr/bin/python

print(hex(20)) # convert int to hex

return the “identity” of an object, which is not the physical address

#!/usr/bin/python

l = [1, 2, 3, 4]
l2 = l
l3 = [1, 2, 3, 4]

print(id(l), id(l2)) # l and l2 have same ids
print(id(l), id(l3)) # l and l3 have different ids

reads a line from input and converts it to a string

#!/usr/bin/python

value = input('Input an integer number: ')
print(int(value)*100)

return an integer from a number or string, return 0 if no arguments are given

#!/usr/bin/python

print(int('10')) # string to int
print(int(3.14)) # float to int
print(int(0b1001)) # binary number to int
print(int(0o1001)) # octal number to int
print(int(0xF1)) # hexadecimal to int

Return an iterator object

#!/usr/bin/python

i = iter(range(10))

try:
    while True:
        print(next(l)) #if no more element, raise StopIteration
except StopIteration:
    pass

Return the length (the number of items) of an object, argument may be a sequence or a collection

#!/usr/bin/python

print(len(range(4))) # 4

print(len({'Name': 'Lin', 'Age': 39})) # 2

return the largest item in an iterable or the largest of two or more arguments

#!/usr/bin/python

m = max([1, 4, 2, 6]) # 6
print(m)

m = max(1, 4, 2, 6) # 6
print(m)

return the smallest item in an iterable or the smallest of two or more arguments

#!/usr/bin/python

m = min([1, 4, 2, 6]) # 1
print(m)

m = min(1, 4, 2, 6) # 1
print(m)

Retrieve the next item from the iterator

#!/usr/bin/python

l = iter(range(10))

try:
    while True:
        print(next(l)); #if no more element, raise StopIteration
except StopIteration:
    print('Reach to the end ...')
    pass

return an integer representing the Unicode code point of that characte

#!/usr/bin/python

print(ord('a'))
print(ord(u'a'))
print(ord(u'\u2020'))

Return a new featureless object

Object is a base for all classes

Has the methods that are common to all instances of Python classes

Does not have a __dict__

o = object
print(p.__doc__)

convert an integer number to an octal string prefixed with “0o”

#!/usr/bin/python

print(oct(9)) # convert int to oct

return a range, instead of a list

#!/usr/bin/python

r = range(0, 10, 1)
print(type(r)) # range
print(len(r)) # 10
print(list(r)) # convert a range to list, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

for e in r:
    print(e, end=' ')
print()

return x to the power y

#!/usr/bin/python

print(pow(2, 3)) # 8

print(pow(2, 3, 3)) #2, pow(2, 3) % 3

print(value1, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

values, can take multiple arguments
sep, default deliminator is a single space
end, end the line with a character, default character is '\n', which changes to a new line
file, argument must be an object with a write(string) method, default is sys.stdout
flush, use buffer or forcibly flushed

#!/usr/bin/python

print('Welcome "Lin" ...') # single quote enclose double quote
print("Welcome 'Lin' ...") # double quote enclose single quote

print("""Welcome "Lin" and 'Yanhua' ...""") # triple quotes enclose single quote and double quote
print('''Welcome "Lin" and 'Yanhua' ...''')

# multiline strings
print("""Welcome to Python,
        Lin and
        Yanhua""")

#!/usr/bin/python

print("Welcome to Python 3!")

print("Welcome "+"to "+"Python 3!") # use string concatenation
print("Welcome", "to", "Python 3!") # automatically add space between arguments

print("%s %s %s!" % ("Welcome", "to", "Python 3")) # use old format style
print("{} {} {}!".format("Welcome", "to", "Python 3")) # use new format style

#!/usr/bin/python

print(1, 2, 3, 4, sep='|') # 1|2|3|4

print(1, end='|') # end the line with a character
print(2, end='|')
print() # change to a new line

f = open("data.txt","w")
print('Hello World!', file=f) # output to a file
f.close()

str, compute the “informal” string representation of an object

repr, compute the “official” string representation of an object, used for debugging and development

#!/usr/bin/python

import datetime 
today = datetime.datetime.now()

# str
s = 'Hello, Geeks.'
print(str(s)) # Hello, Geeksl
print(str(2.0/11.0)) # 0.1818
print(str(today)) # 2019-02-04 23:21:52.332522

# repr
s = 'Hello, Geeks.'
print(repr(s)) # 'Hello, Geeks.'
print(repr(2.0/11.0)) # 0.1818
print(repr(today)) # datetime.datetime(2019, 2, 4, 23, 21, 52, 332522)

Return a reverse iterator

#!/usr/bin/python

l = [1, 2, 3, 4]

a = reversed(l) # <class 'list_reverseiterator'>
print(list(a)) # [4, 3, 2, 1]
print(list(a)) # [], a has been consumed

b = reversed(range(4)) # <range_iterator object at 0x10583b9f0>
print(list(b)) # [3, 2, 1, 0]
print(list(b)) # [], b has been consumed

Return number rounded to ndigits precision after the decimal point

round(3.14) # 3
round(3.1415926, 2) # 3.14

is used to slice a given sequence

#!/usr/bin/python

s = slice(1, 10, 2)

l = range(10)
print(list(l[s])) # [1, 3, 5, 7, 9]

l2 = list(range(10))
print(l2[s]) # [1, 3, 5, 7, 9]

return a new sorted list from the items in iterable

#!/usr/bin/python

# sort list
l = [1, 5, 3]
l2 = sorted(l) # only sort the objec with the same data type
print(l2) # [1, 3, 5]

# sort tuple
l = (1, 5, 3)
l2 = sorted(l)
print(type(l2)) # list
print(l2)

# sort dict
d = {'Name': 'Zara', 'Age': 7, 'Class': 'First'}
d2 = sorted(d) # return a list containing the sorted keys
print(d2) # ['Age', 'Class', 'Name']

Return a str version of object

#!/usr/bin/python

print(str(10)) # int to str
print(str(3.14)) # float to str
print('{0:#b}'.format(0b1001)) # binary number to str

returns the total of an iterable

#!/usr/bin/python

a = range(10)

print(sum([1, 2, 3, 4])) # 10
print(sum([1, 2, 3, 4], 1)) # 1 + 2 + 3 + 4 + 1

return the type of an object

#!/usr/bin/python

print(type('Hello World!')) # str

Return the __dict__ attribute for a module, class, instance, or any other object with a __dict__ attribute

#!/usr/bin/python

class Vehicle(object):
    def __init__(self, maker, year):
        self.maker = maker
        self.year = year

def main():
    v = Vehicle('Buick', 1998)

    d = vars(v)
    print(d) # {'maker': 'Buick', 'year': 1998}
    print(vars(Vehicle)) # {'__module__': '__main__', '__init__': <function Vehicle.__init__ at 0x10daee2f0>, '__dict__': <attribute '__dict__' of 'Vehicle' objects>, '__weakref__': <attribute '__weakref__' of 'Vehicle' objects>, '__doc__': None}

if __name__ == '__main__':
    main()

Make an iterator that aggregates elements from each of the iterables

#!/usr/bin/python

x = [1, 2, 3]
y = [4, 5, 6]
zipped = zip(x, y)

print(list(zipped)) # [(1, 4), (2, 5), (3, 6)]

Built-in Functions