Python numbers, strings, lists, Ganso, dictionaries, collections

I. Digital

Python supports three different numeric types:

• Integral type (INT): No size limit for integers. (python3.x), also available in 16 binary or octal notation.
• Float type (float): can also be represented by scientific notation (2.5e2 = 2.5 x 102 = 250)
• Complex number ((complex)): A + BJ, or complex (a, B), indicates that both real and imaginary B of a complex number are floating-point types.

Numeric Type conversions:

• int (x) converts x to an integer.

• Float (x) converts the x to a floating-point number.

• Complex (x) converts x to a complex number, the real part is x, and the imaginary part is divided into 0.

• Complex (x, Y) converts X and Y to a complex number, the real part is x, and the imaginary part is Y. X and y are numeric expressions.

Numerical calculation:

>>> 17/3   # Integer division returns floating-point 5.666666666666667>>>>>> 3  # Integer division Returns the result of rounding down 5>>> 3   #% operator returns the remainder of division 2>>> 5 * * 2   # 5 squared 25

　　

Mathematical functions:

function	return value (description)
ABS (x)	Returns the absolute value of a number, such as ABS (-10) returns 10
Ceil (x)	Returns the top integer of a number, such as Math.ceil (4.1) returns 5
CMP (x, y)	If x < y returns 1, if x = = y returns 0, if x > y returns 1. Python 3 is deprecated . Replace with use (x>y)-(x<y) .
EXP (x)	Returns the x power of E (ex), such as MATH.EXP (1) returns 2.718281828459045
Fabs (x)	Returns the absolute value of a number, such as Math.fabs (-10) returns 10.0
Floor (x)	Returns the lower integer of a number, such as Math.floor (4.9) returns 4
Log (x)	If Math.log (MATH.E) returns 1.0,math.log (100,10) returns 2.0
LOG10 (x)	Returns the logarithm of x with a base of 10, such as MATH.LOG10 (100) returns 2.0
Max (x1, x2,...)	Returns the maximum value of a given parameter, which can be a sequence.
Min (x1, x2,...)	Returns the minimum value for a given parameter, which can be a sequence.
MODF (x)	Returns the integer portion of x and the fractional part, the two-part numeric symbol is the same as x, and the integer part is represented by a floating-point type.
Pow (x, y)	The value after the x**y operation.
Round (x [, N])	Returns the rounded value of the floating-point number x, if given an n value, that represents the digits rounded to the decimal point.
sqrt (x)	Returns the square root of the number x.

Random number function:

Random numbers can be used in mathematics, games, security and other fields, but also often embedded in the algorithm to improve the efficiency of the algorithm and improve the security of the program. Python contains the following common random number functions:

function	Description
Choice (seq)	Pick an element randomly from the elements of the sequence, such as Random.choice (range (10)), and randomly pick an integer from 0 to 9.
Randrange ([Start,] stop [, step])	Gets a random number in the collection that increments by the specified cardinality from the specified range, and the base default value is 1
Random ()	Randomly generates the next real number, which is within the [0,1] range.
Seed ([x])	Changes the seeding seed of the random number generator. If you don't know how it works, you don't have to specifically set Seed,python to help you choose Seed.
Shuffle (LST)	Randomly sort all elements of a sequence
Uniform (x, Y)	Randomly generates the next real number, which is within the [x, Y] range.

Trigonometric function:

function	Description
ACOs (x)	Returns the inverse cosine radian value of x.
ASIN (x)	Returns the arc value of the arc sine of X.
Atan (x)	Returns the arc tangent value of x.
Atan2 (y, x)	Returns the inverse tangent value of the given X and Y coordinate values.
COS (x)	Returns the cosine of the arc of X.
Hypot (x, y)	Returns Euclidean norm sqrt (x*x + y*y).
Sin (x)	Returns the sine of the X radian.
Tan (x)	Returns the tangent of x radians.
Degrees (x)	Convert radians to angles, such as degrees (MATH.PI/2), returns 90.0
Radians (x)	Convert an angle to radians

Numeric constants:

Constants	Description
Pi	Mathematical constant Pi (pi, usually denoted by π)
E	The mathematical constant e,e is the natural constant (natural constant).

Two. String

Python Relay literal characters:

Escape Character	Description
\ (at end of line)	Line continuation character
\\	Backslash symbol
\‘	Single quotation marks
\"	Double quotes
\a	Bell
\b	BACKSPACE (Backspace)
\e	Escape
\000	Empty
\ n	Line break
\v	Portrait tab
\ t	Horizontal tab
\ r	Enter
\f	Page change
\oyy	Octal number, the character represented by YY, for example: \o12 for newline
\xyy	Hexadecimal number, the character represented by YY, for example: \x0a for line break
\other	Other characters are output in normal format

String built-in functions:

Serial Number	Method and Description
1	Capitalize () Converts the first character of a string to uppercase
2	Center (width, Fillchar) Returns a string that specifies the width of the center, Fillchar is a filled character, and the default is a space.
3	Count (str, beg= 0,end=len (String)) Returns the number of occurrences of STR in a string, if beg or end specifies that the number of STR occurrences in the specified range is returned
4	Bytes.decode (encoding= "Utf-8", errors= "strict") There is no Decode method in Python3, but we can use the decode () method of the Bytes object to decode the given bytes object, which can be encoded back by bytes ().
5	Encode (encoding= ' UTF-8 ', errors= ' strict ') Encodes a string in the encoded format specified by encoding, if an error defaults to a ValueError exception unless errors specifies ' ignore ' or ' replace '
6	EndsWith (suffix, beg=0, End=len (String)) Checks whether the string ends with obj, or returns False if beg or end specifies whether to end with obj in the specified range, or True if it is.
7	Expandtabs (tabsize=8) Turns the tab symbol in string strings to a space, and the default number of spaces for the tab symbol is 8.
8	Find (str, beg=0 End=len (String)) Detects if STR is contained in a string, and if the range beg and end is specified, the check is contained within the specified range and returns 1 if it contains the index value that returns the start.
9	Index (str, beg=0, End=len (String)) Just like the Find () method, only if STR does not report an exception in the string.
10	Isalnum () Returns True if the string has at least one character and all characters are letters or numbers, otherwise False
11	Isalpha () Returns True if the string has at least one character and all characters are letters, otherwise False
12	IsDigit () Returns True if the string contains only a number, otherwise False:
13	Islower () Returns True if the string contains at least one case-sensitive character, and all of these (case-sensitive) characters are lowercase, otherwise False
14	IsNumeric () Returns True if the string contains only numeric characters, otherwise False
15	Isspace () Returns True if the string contains only white space, otherwise False.
16	Istitle () Returns True if the string is heading (see Title ()), otherwise False
17	Isupper () Returns True if the string contains at least one case-sensitive character, and all of these (case-sensitive) characters are uppercase, otherwise False
18	Join (SEQ) Merges all elements of the SEQ (the string representation) into a new string with the specified string as a delimiter
19	Len (String) return string length
20	Ljust (width[, Fillchar]) Returns a string that is left-justified by using Fillchar to fill a new string of length width, and fillchar the default is a space.
21st	Lower () Converts all uppercase characters in a string to lowercase.
22	Lstrip () Truncates the left space of the string or specifies the character.
23	Maketrans () To create a conversion table of character mappings, for the simplest invocation of two parameters, the first argument is a string representing the character that needs to be converted, and the second argument is the target of the string representation of the transformation.
24	Max (str) Returns the largest letter in the string str.
25	Min (str) Returns the smallest letter in the string str.
26	Replace (old, new [, Max]) Replace the str1 in the string with str2, and if Max specifies it, the replacement does not exceed Max times.
27	RFind (str, Beg=0,end=len (String)) Similar to the Find () function, it is just looking from the right.
28	Rindex (str, beg=0, End=len (String)) Similar to index (), but starting from the right.
29	Rjust (width,[, Fillchar]) Returns the right alignment of an original string and fills a new string of length width with Fillchar (default space)
30	Rstrip () Removes a space at the end of a string string.
31	Split (str= "", Num=string.count (str)) Num=string.count (str)) intercepts a string with the Str delimiter, and only the NUM substring if NUM has a specified value
32	Splitlines ([keepends]) Separated by rows (' \ r ', ' \ r \ n ', \ n '), returns a list containing the rows as elements, if the argument keepends is False, does not contain a newline character, and if true, the newline character is preserved.
33	StartsWith (str, Beg=0,end=len (String)) Checks whether the string starts with obj, returns True, or False. If beg and end specify a value, the check is within the specified range.
34	Strip ([chars]) Execute Lstrip () and Rstrip () on a string
35	Swapcase () Convert uppercase in a string to lowercase, lowercase to uppercase
36	Title () Returns the "heading" string, meaning all words start with uppercase and the remaining letters are lowercase (see istitle ())
37	Translate (table, deletechars= "") Converts a string character to a table (containing 256 characters) given by STR, and the character to be filtered out into the Deletechars parameter
38	Upper () lowercase letters in a converted string are capitalized
39	Zfill (width) Returns a string of length width, the original string right-aligned, front padding 0
40	Isdecimal () Checks whether the string contains only decimal characters and returns False if true.

Three. List

Functions for common list of operations:

Serial Number	function
1	Len (list) Number of list elements
2	Max (list) Returns the maximum value of a list element
3	MIN (list) Returns the minimum value of a list element
4	List (seq) Convert a tuple to a list

Common ways to manipulate lists:

Serial Number	Method
1	List.append (obj) Add a new object at the end of the list
2	List.count (obj) Count the number of occurrences of an element in a list
3	List.extend (seq) Append multiple values from another sequence at the end of the list (extend the original list with a new list)
4	List.index (obj) Find the index position of the first occurrence of a value from the list
5	List.insert (index, obj) Inserting an object into a list
6	List.pop (Obj=list[-1]) Removes an element from the list (the last element by default), and returns the value of the element
7	List.remove (obj) To remove the first occurrence of a value in a list
8	List.reverse () Reverse List of elements
9	List.sort ([func]) Sort the original list
10	List.clear () Clear List
11	List.copy () Copy List

Four. Yuan zu

A Python tuple is similar to a list, except that the elements of a tuple cannot be modified.

Tuples use parentheses, and the list uses square brackets.

T1 = (1,)  # Ganso of a single element t2 = ()  # empty Progenitor

　　

Five. Dictionaries

Built-in functions for dictionaries:

Serial Number	Functions and descriptions
1	Radiansdict.clear () Delete all elements in a dictionary
2	Radiansdict.copy () Returns a shallow copy of a dictionary
3	Radiansdict.fromkeys () Create a new dictionary with the keys to the dictionary in sequence seq, Val is the initial value corresponding to all keys in the dictionary
4	Radiansdict.get (Key, Default=none) Returns the value of the specified key if the value does not return the default value in the dictionary
5	Key in Dict Returns False if the key returns true in the dictionary Dict
6	Radiansdict.items () Returns an array of traversed (key, value) tuples as a list
7	Radiansdict.keys () Returns a dictionary of all keys in a list
8	Radiansdict.setdefault (Key, Default=none) Similar to get (), but if the key does not exist in the dictionary, the key is added and the value is set to default
9	Radiansdict.update (DICT2) Update the key/value pairs of the dictionary dict2 to the Dict
10	Radiansdict.values () Returns all values in the dictionary as a list
11	Pop (Key[,default]) Deletes the value of the dictionary given key key, and returns the value to be deleted. The key value must be given. Otherwise, the default value is returned.
12	Popitem () Randomly returns and deletes a pair of keys and values in the dictionary (typically delete the end pair).

Six. Collection

Python numbers, strings, lists, Ganso, dictionaries, collections