Essay:
A programming language
1. What is the programming language?
Expression can be recognized by a computer programming language mentioned above, i.e., language communication medium, and a computer programming language to communicate with a programmer medium. In the programming world, a computer is more like a slave to the purpose of human programmed to command the slaves to work.
2. What is programming?
Programming that is based on the needs of programmers to write down their thoughts flow in accordance with the syntax of a programming language style, the result is the output file that contains a bunch of characters.
Emphasize:
Before the program is not running with the ordinary file is no different, only at run time, the characters written in the document have specific grammatical meaning.
The second computer part
CPU
RAM
External memory
input device
Output Device
Installation and use of three of python
1. Install the python interpreter
2. Install pycharm Editor
3. Write python code and output print hello world!
print('hello world')
Four Variable
Variables: the amount may change.
1. Variable values: a real memory address stored in the memory, 'tank', is generated in memory - the memory address parts. .
2. Variable name: value for the variable binding relationship, the equivalent of a house number, used to bind variables.
3 =: variable value used to bind to the variable.
4. Assignment = No: Binding the value of the variable to the variable name.
name = 'apple'
print(name)
The variable naming convention:
Hump nomenclature: AgeofTank
Note: python is strongly recommended to use an underscore name: age_ of_ tank
6. The variable names defined specifications:
To begin with a letter or an underscore English name (name can not start with a number 1a and error !!!)
For example: a letters beginning ab, start with an underscore _ab;
Keywords can not be named:
例如： 'and', 'as',’assert', 'break', ’ class',’ continue'，'def’, 'de1',’elif', 'else',
'except', 'exec' ,’finally', 'for'，'from'，'global', 'if', 'import'，in',’ is'，
'lambda', 'not'， 'or’，'pass'，'print',’raise'， ’return',’try', while', 'with'，'yield'
7. Define the variable names a bad way:
a. Do not Chinese name
b. the variable name is too long
c. variable terms do not convey
8. The definition of a variable three characteristics:
name = 'apple' name2= 'apple '
print(id(name))
print(id(name2))
name1 ='hello' print(type(name1))
name2= 'hello' print(name1==name2)
Five constants
Not change amount.
Named to all uppercase.
Not can not modify them, but everyone who ordained all uppercase variables are called constants, can not be modified.
= SCHOOL ' College '
Six user to interact with the program
Input (any type of data input and output of the input string are):
input()
Output:
print()
= the INPUT name ( ' Please enter the name: ' ) Print (name)
Seven formatted output
Dear customer, hello! Your month deducted 99 yuan bill, left 0.
# By some placeholder character for a location in the replacement string.
Placeholder:
% S: can replace any type
% D: can be replaced by a digital type
Example:
Dear customer, hello! Your phone bill this month deducted yuan% s,% d remaining yuan.
Eight basic data types
1. Digital Type:
Integer: int
Float: float
2. String type
Role: name, sex, nationality, address and other descriptive information
Definition: single quotation marks \ double quotes \ three marks, a string of characters
name='tank'
Master priority actions:
1, according to an index value (forward + reverse take take): can only take
# Forward taken: str1 = ' Hello World ' Print (STR [0]) # H Print (STR [. 9]) # R & lt # Reverse taken: Print (str1 [-2]) # L
2, a slice (care regardless of the end, step)
# 5-1 length str1 = ' Hello World ' Print (STR [0:. 5]) # Hell # step Print (STR [0: 12 is: 2]) # hl0wrd
3, the length len
print (referred to as (str1))
4, members and not in operation in
print('h' in str1) #True
5, remove the blank strip
# Shift left: str1 = ' Hello ' Print (str1.strip ()) # remove the specified character str2 = ' Hello!! ' Print (str2.strip ( ' ! ' ))
6, slicing split
str1='hello world ' print(str1.split('')) #['hello','world']
7, circulation
for line in str1: print(line)
You need to know:
1, strip, lstrip (removed the left margin), rstrip (remove blank on the right), it is the same usage
2, lower (all lowercase inflicted), upper (both ended up capital)
3, startswith (determined character is equal to the value at the beginning of the input), endswith (end determines whether or equal)
4, format three games are played
The position of formatted
According to the index format
By name format
5, split (slice), rsplit
6, join (string concatenation, string concatenation only)
7, replace (string replacement)
8, isdigit (numeric string is determined)
= str1 ' Hello World ' # . 1, Print (str1.strip ()) Print (str1.rstrip ()) # right of Print (str1.lstrip ()) # left # 2, Print (str1.lower ()) # lowercase Print (str1.upper ()) # D = uppercase # . 3, Print (str1.startswith ' Hello ' )) # True Print (str1.endswith ( ' LD ' )) # True # . 4, #4.1 Print ( ' name {}, Age {} ' .format ( ' Apple ' , 12 is )) # 4.2 Print ( ' name {0}, Age {}. 1 ' .format ( ' Apple ' , 12 is )) # 4.3 Print ( ' name {name}, Age Age {} ' .format (Age = 12 is, name = ' Apple ' )) # sequence can easily # . 5 Print (str1.split ( '' )) # . 6 Print ( ' '.join(['apple','12','from anhui'])) #7 str2=str1.replace('hello','people') print(str2) #8 choice=input('功能[0][1][2]:') print(choice.isdigit())
Nine comments
Single-line comments: #
shortcuts: ctrl + /
Multi-line comments: triple quotes "" "" "
shortcuts:
'' ' + Enter key
" '" + Enter key
Classwork:
= name ' Alex ' # . 1) removed on both sides of the value corresponding to the variable name spaces, and outputs the processing result Print (name.strip ()) # 2) determines whether the value corresponding to the variable name beginning with "al", and outputs the result Print (name.startswith ( ' Al ' )) # . 3) determines whether the value of the corresponding variable name ending in "X", and outputs the result Print (name.endswith ( ' X- ' )) # . 4) to a value corresponding to the variable name the "l" is replaced with "p", and outputs the result NAME2 = name.replace ( ' L ' , ' P ' ) Print (NAME2) # . 5) the variable name corresponding to segmentation according to "l", and outputs the result . Print (name.L ' )) # . 6) corresponding to the name of the variable value becomes capital, and outputs the result Print (name.upper ()) # . 7) corresponding to the name of the variable value becomes lower case, and outputs the result Print (name.lower ()) # ? 8) make the output value of the name variable corresponding to the second character Print (name [2 ]) # . 9) Please outputs the first three characters values name corresponding variable? Print (name [0:. 4 ]) # 10 ) Please outputs two character value corresponding to the variable name? Print (name [-3: -1 ]) Print (name [-1 ]) # . 11) requested output value corresponding to the variable name index where "e" position ? NAME2 = name.strip ( ' the X- ' ) Print (len (NAME2)) #12) acquisition sequences, removing the last character. Such as: oldboy then get oldbo. Print (name.strip ( ' X- ' ))
result:
