A computer part: CPU, memory, external storage, input devices, output devices
Second, the installation and use of
1, the python interpreter installation
2, mounting editor python
3. Create a python file, print hello world!
Third, what is variable
Variables: the amount of change
Variable value: "tank", will produce a memory address in memory
Variable names: Pretty bound with a house number for the variable
=: Variable value used to bind to the variable
name = "tank" print(name)
Naming variables
Hump nomenclature: AgeOfTank
Underline name: age_of_tank #python strongly recommended
Variable names defined specification
1, to start with an English letter or an underscore named
English alphabet begins with al #
_al # start with an underscore
2, can not begin with a numeric name
1a # error
3, the keyword can not be named
'and','as','assert','break','class','continue','def','del','elif','else','except','exec','finally','for','from','global','if','import'
Defined variable names a bad way
1, not to Chinese name
2, the variable name is too long
3, variable terms do not convey
Three features define the variables:
id: The value of the variable used to represent only a memory address in memory
type: type of variable values
value: value of the variable
Third, the constant
constant:
It refers to the same amount
The constant nature is variable in python does not have any mechanism to limit that you can not modify a constant,
But python program to artificially limit yourself to meet all uppercase variables can not be modified to
Naming conventions:
Variable names all uppercase
SCHOOL = 'Hefei'
Fourth, the user interacts with the program
Input:
python3: input()
python2:
Output: print ()
V. Notes
Single-line comments: # shortcuts: ctrl + /
Multi-line comments: triple quotes' '' '' 'shortcuts:' '' + Enter key "" "+ Enter key
Sixth, the basic data types
Digital Type:
1, plastic: int
2, floating point type: float
String Type: str
Priority control operation
1, according to an index value (forward + reverse take take): can only take
2, a slice (care regardless of the end, step)
3, the length len
4, members and not in operation in
5, remove the blank strip
6, slicing split
7, circulation
Seven formatted output
Dear customer, hello! Your month deducted 99 yuan bill, left 0 yuan
# 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
operation
name = ' a1eX'
1, both sides of the removed name spaces corresponding to the variable value, and outputs the processing result
name = ' a1eX' print(name.strip())
2, it is determined whether the variable name value that corresponds to 'a1' at the beginning, and outputs the result
name = ' a1eX' print(name.startswith('a1'))
3, it is determined whether the value corresponding to the variable name to 'X' at the end, and outputs the result
name = ' a1eX' print(name.endswith('X'))
4, the value of the variable name corresponding to the '1' is replaced with 'P', and outputs the result
name = ' a1eX' name1 = name.replace('1', 'p') print(name1)
5, the variable name according to the corresponding value '1' is divided, and outputs the result
name = ' a1eX' print(name.split('1'))
6, the corresponding value becomes the variable name in uppercase, and outputs the result
name = ' a1eX' print(name.upper())
7, the name variable value corresponding to lower case, and the output
name = ' a1eX' print(name.lower())
8, please outputs of the two character values corresponding to the variable name?
name = ' a1eX' print(name[1])
9, please output the first three characters of the name value of the corresponding variable?
name = ' a1eX' print(name[0:3])
10, please output the value of two variables corresponding character name?
name = ' a1eX' print(name[-2:])
11, output a value corresponding to the variable name index position 'e' where?
name = ' a1eX'
print(name.index('e'))
12, to obtain sequences, removing the last character. The; Oldboy is acquired oldbo.
name = ' a1eX' print(name[:-1])