Python basic summary article

Variables and Data Types

Numbers digital divided: int int, long long integer, float float, complex complex

String character string by the string of numbers, letters, the underscore, for indicating the data type of text

bool Boolean: True, False, for making a judgment (True actual value is 1, False actual value is 0)

List List support characters, numbers, strings containing a list (i.e. nested), with [] identification, sequence object

Tuple tuples, with () ID, not the second assignment, as will be appreciated immutable list (read-only list), ordered objects

Dict dictionary, with {} identified by the index (key) value and a value corresponding to its composition, unordered objects

Simple data type conversion

int (x) function: The x into an integer, if rounding is round (x) function
float (x) function: x into the float
STR (x) function: into a string of x

Sequence and strings

Sequence and the general procedure

Print (LST1 + lst2)   # "+": the sequence link 

Print (LST1 *. 3, lst2 * 2)   # "*": sequence repeats 

Print (LST [0], LST [2], LST [. 9])   # Index starts from 0, EG lst [2], the subscript index is 2, the third point value lst 

Print (lst [-1])   # index value -1 is the last 

Print (lst [2:. 5])   # slice will be appreciated that the value of the interval as a list, and a left-closed right-open interval, where lst [2: 5] interval represents: index 2 - the index value of 4 

Print (LST [0:. 5: 2])   # List [I: J: n] Representative: index i - index j, as in steps n

Feature list

It may comprise any type of objects: numbers, strings, lists, etc.
By sequentially access sequence index value index → sequence can not be changed, through the index to locate an element of the list
Be free to change the length of the list, the new list corresponding to the specified arbitrary
Nestable
Situ change
List generator: range () is a generator, it points to a range #range (0,10,2) of the representative points 0,2,4,6,8 these values represents the final step

The variable list list common operations

list.append () to add elements
Add multiple elements with .extend () method: with a new list of extensions of the original list (direct expansion)
.remove method: remove the first occurrence of a value in the list
del statement: delete the list of corresponding index values
lst.clear () : Removes all values
x.insert (i, m) Method: inserting the index i m, i where the index of (i + 1) th value represents
list.copy () method: Copy a new list (pointing to the two lists)
.sort () : Default ascending sort / alphabetically (parameter reverse: reverse the order, for digital)
Function sorted () : Sort and copy

String associated notes

Double quotes single quotes no difference, but when a quoted text to alternately use
Need more time with three rows quoted string '' '' '' "" "" ""

Escape character

\ ", \": Outputs single double quotes
\ N: an empty line
Output \, the file path with "/" or "\\"
Extending - # local file read and write data to define: a point to locally stored file, or a link to a map
path1 = 'C: /Users/Hjx/Desktop/text.txt' # single backslash: /
path2 = 'C: \\ Users \\ Hjx \\ Desktop \\ text.txt' # two slashes: \\ (first \ is the escape character)
path3 = r'C: \ Users \ Hjx \ Desktop \ text.txt '# r for preventing the escape character

Sequence common functions

in / not in: determining whether there is
Text Links: print ( 'I am handsome' + "Yes"
Copy Text: print ( 'handsome' * 4)
.index () Method: print (st.index ( 'g'
String length is calculated: len ()

Common features of the string

.replace (Old, new new, COUNT) : modify the string, count: replace several
.split (obj) : split string, a list of
.join () : the connection string, object list
.startswith ( "xie") determines whether to "xie" begin; if str.endswith ( "xie") is determined to "xie" end
.upper () all caps
.lower () all lowercase
.swapcase () invert case
.capitalize () first letter capitalized
.isnumeric () If the string contains only digit returns True, otherwise False
.isalpha () if there is at least one character string and all the characters are the letters return True, otherwise False
.rstrip () delete the character at the end of the space
% s% i% f are formatted string, s / i / f represent the source data string is inserted Type: integer / character / float
% +. 2f output plus two decimal places and displays % e% E
% g less scientific notation of decimal floating-point number automatically when the identification data when the automatic recognition complex scientific notation

# More powerful formatting method .format 

Print ( " the User ID: {0} " .format ( " the root " ))
 Print ( " {}} Oh { " .format ( " A " , " B " ))
 # { } here placeholder for which there may be no digital 

Print ( " {} {} {} " .format ( ' A ' , ' B ' , ' C ' ), ' \ n- ' ,
 "{0}{1}{2}{0}".format ( ' A ' , ' B ' , ' C ' ), ' \ n- ' )
 # Print ( "{} {} {} {}." the format ( 'A', 'B', 'C')) 
# {0} and {} distinction: are placeholders, which has explicitly 

Print ( " my job is work} { " .format (= work ' design ' ))
 # can also be used to indicate a variable