Built-in function
What's a built-in function? It's a tool that Python provides for us to use directly, such as our print,input,type,id, etc. Up to version 3.6.2 of python.
There are 68 built-in functions. They are provided directly by Python to us. Some of them have been used. Some of them have not been used yet. Another one is that we need to finish learning object-oriented to continue learning. Today, let's take a look at python's built-in functions.
Scope correlation
locals() Returns the name in the current scope
globals() Returns the name in global scope
Iterator correlation
range() Generate data
The next() iterator executes downward once, and the u next_() method is actually used internally to return to the next item of the iterator
iter() Gets the iterator, which is actually acquired internally using the u iter_() method
Execution of string type code
eval() executes string-type code and returns the final result
print(eval('2+8'))
Result:
10
n = 8
print(eval('n + 10'))
Result:
18
exec() executes code of string type
exec('''
for i in range(10):
print(i)
''')
# We write code in a python-recognizable grammar, and this time we write strings that can be executed as well.
exec('''
def func():
print("444")
func()
''')
//Result:
444
compile() mutates the code of the string type, and the code object can be executed by an exec statement or evaluated by eval().
'''
//Description of parameters:
1.resource #Method to execute code, dynamic code fragments
2.file name,File Name for Code Storage,When the first parameter is passed in,Just leave this parameter blank.
3.Pattern,There are three values
1.exec When putting some process statements in general
2.eval resource Store only one evaluation expression
3.single resource When the stored code interacts.mode Should be single
'''
code = 'for i in range(10):print(i)'
c1 = compile(code,'',mode='exec')
exec(c1) # No return value with exec
code1 = '1+2+4'
c2 =compile(code1,'',mode='eval')
a = eval(c2) # Use eval to have a return value
print(a)
code = 's = input("Please enter the content");print(s)'
c1 = compile(code,'',mode='single')
exec(c1) #No return value with exec
Through the above test, we found that as long as exec has no return value, eval has return value, compile is not very common.
Input-output correlation
input() Gets user input
print() Print Output
Memory related
hash() Gets the hash value of the object (int.str,bool,tuple)
id() Gets the memory address of the object
Document operation related
open() is used to open a file and create a file handle
Module correlation
_u import_() for dynamically loading classes and functions
Help
help() Functions are used to view detailed descriptions of functions or module uses
Call correlation
callable() is used to check whether an object is callable. If it returns True, the object may fail. If it returns False, the call is absolutely complete.
View memory properties
dir() Views the built-in attributes of an object by accessing the u dir_() method of the object
Basic data type correlation
Number correlation:
bool() Converts the given data to a bool value, if no value is given. Returns False
int() Converts the given data to an int value and returns 0 if no value is given
float() converts a given data into a float value, which is the last decimal
Compoilex () creates a complex number. The first parameter is the real part, the second parameter is the imaginary part. Or the first parameter describes the complex number directly with a string.
Binary conversion:
bin() Converts the given parameters to binary
otc() converts the given parameters into octal
hex() converts the given parameters into hexadecimal
Digital operations:
Absolute value of ABS
divmode() returns quotient and remainder
Round (rounding)
pow(a,b) calculates the B power of A. If there is a cubic parameter, then the number of third parties is redundant after the 10,000 power.
sum() summation
Minimum value
max() Maximum
Data structure correlation
Lists and meta-ancestors
list() Converts an iterative object into a list
tuple() converts an iterative object into a meta-ancestor
reverse() inverts a sequence and returns the iterator of the inverted sequence
Slice (slice) slices of the list
a = Hello, everybody. I'm Wusong. s1 = slice(1,8,2) print(a[s1]) Result: Home I Wu
String correlation:
str() Converts data into strings
Form () is related to specific numbers, used to calculate various decimal, actuarial, etc.
Character string
# Character string
# print(format('meet','<20')) #Left alignment
# print(format('meet','>20')) #Right alignment
# print(format('meet','^20')) #Centered
//Result:
meet
meet
meet
numerical value
#numerical value print(format(3,'b')) # Binary system print(format(97,'c')) # Converting to unicodezif print(format(11,'d')) #Decimal system print(format(56)) #Same as d. print(format(11,'n')) #Decimal system print(format(11,'o')) #Octal number system print(format(11,'x')) # Hexadecimal (lowercase) print(format(11,'X')) # Hexadecimal (capital letter) # Floating point number print(format(1234567890,'e')) #Scientific computing, default 6 bits print(format(123456789,'0.2e'))# Scientific calculation, keep 2 decimal places (lowercase) print(format(123456789,'0.2E'))# Scientific calculation, keep 2 decimal (upper case) print(format(1.23456789,'f')) #The decimal point counting method, reserving 6 decimal places print(format(1.23456789,'0.2f')) # Decimal point counting method, reserve 2 digits print(format(1.23456789,'0.10f')) # Decimal point counting method, reserve 2 digits print(format(1.23456789e+1000,'F')) # Decimal point counting method
bytes() Converts strings to bytes types
s = 'Hello, Wu Da.'
bs = s.encode('utf-8')
print(bs)
//Result: b' xe4 xbd xa0 xe5 xa5 xbd xe6 xad xa6 xe5 xa4 xa7'
s1 = bs.decode('utf-8')
print(s1)
//Result: Hello Wuda
bs = bytes(s,encoding='utf-8')
print(bs)
//Result: b' xe4 xbd xa0 xe5 xa5 xbd xe6 xad xa6 xe5 xa4 xa7'
//Encoding strings into utf-8
bytearray() returns a new byte array in which the elements are variable and the values of each element range from 0 to 256.
ret = bytearray('meet',encoding='utf-8')
print(ret)
print(ret[0])
//Result:
bytearray(b'meet')
109
momoryview() View bytes'memory address
s = memoryview('Gentiana'.encode('utf-8'))
print(s)
# Result:
# <memory at 0x000001F332E0E288>
ord() Input character locates with character encoding
print(ord('a'))
print(ord('in'))
print(ord('country'))
Result:
97
20013
22269
Corresponding to the current encoding
chr() Input the position number to find the corresponding character
print(chr(97)) # Find the corresponding character print(chr(20013)) # Find the corresponding character # Result: a //in
ascii() is the return value in ascii code, not to return\ u
print(ascii('a')) determines that the string is not in the ASCII code table
print(ascii('zhong'))
Result:
'a'
If'__ 4e2d'does not exist, ret u rn to ___________________________
repr() returns the form of an object's essence
name = 'alex' Print (repr (name)# returns the representation of the object's essence Result: 'alex' Name ='My name is% r' Print (name%'meet')% R is repr Result: My name is'meet'.
Data set
dict() Create a dictionary
set() Creates a collection
frozenset() creates a frozen collection that cannot be added or deleted
Other related
len() returns the number of elements of an object
enumerate() Gets the enumeration object
lst = ['alex','wusir','taibai']
for i,k in enumerate(lst):
print('This is the serial number.',i)
print('This is the element.',k)
all() All of the iteratable objects are True, and the result is True.
lst = [1,2,3,4,True,0,False] lst1 = [1,2,3,4,True] print(all(lst)) print(all(lst1)) //Result: False True
any() One of the iteratable objects is True, which is True.
lst = [1,2,3,4,True,0,False] lst1 = [1,2,3,4,True] print(any(lst)) print(any(lst1)) //Result: False True
The zip() function is used to take an iterative object as a parameter and package the corresponding elements in the object into a meta-ancestor.
It then returns the contents consisting of these meta-ancestors. If the number of elements in each iterator is not the same, it returns in the shortest length.
lst1 = [1,2,3]
lst2 = ['a','b','c','d']
lst3 = (11,12,13,14,15)
for i in zip(lst1,lst2,lst3):
print(i)
//Result:
(1, 'a', 11)
(2, 'b', 12)
(3, 'c', 13)
Lecture after lambda
sorted() sort iterative objects
filter() filtering
map() maps the specified sequence according to the function provided
See material
https://www.processon.com/view/link/5b4ee15be4b0edb750de96ac