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chapter
- Python Introduction
- Python development environment to build
- Python syntax
- Python variables
- Python Value Type
- Python type conversion
- Python String (String)
- Operators Python
- Python list (list)
- Python tuples (Tuple)
- Python collection (Set)
- Python dictionary (Dictionary)
- Python If … Else
- Python While loop
- Python For loop
- Python functions
- Python Lambda
- Python Classes and Objects
- Python inheritance
- Python iterator (Iterator)
- Python module
- Python date (Datetime)
- Python JSON
- Python regular expression (RegEx)
- Python PIP package manager
- Python exception handling (Try ... Except)
- Python Open File (File Open)
- Python read file
- Python write file
- Python delete files and folders
If Python conditions and statements
Python supports common mathematical logic conditions:
- equal:
a == b - not equal to:
a != b - Less than:
a < b - Or less:
a <= b - more than the:
a > b - greater or equal to:
a >= b
These conditions can be used in a variety of statements, the most common is to use the "if statement" and the loop statement.
Examples
If the statement
a = 99
b = 100
if b > a:
print("b 大于 a")
indentation
Python dependent indentation (spaces) to define the scope of the code. Other programming languages commonly used braces.
Examples
If the statement is not indented cause errors:
a = 99
b = 100
if b > a:
print("b 大于 a") # 此处会报错
elif
In python, elifkeyword, he said: "If the preceding conditions are not met, then try this condition" means.
Examples
a = 99
b = 99
if b > a:
print("b 大于 a")
elif a == b:
print("a, b相等")
In this example, a equals b, so the first condition is not met, then the elifcondition is true, is printed to the screen: a, equal b.
else
In python, elsekeyword, he said: "If the preceding conditions are not true, then ...."
Examples
a = 100
b = 99
if b > a:
print("b 大于 a")
elif a == b:
print("a, b相等")
else:
print("a 大于 b")
In this example, a ratio b large, so the first condition is not met, elifthe conditions are not established, so go to elseprint to the screen is: a is greater than b.
No elifof elseit is possible:
Examples
a = 100
b = 99
if b > a:
print("b 大于 a")
else:
print("b 不大于 a")
Compact if statement
If only one statement if the latter statement to be executed, you can put it in one line with the If statement.
Examples
Line if statement:
if a > b: print("a is greater than b")
Compact if ... else statement
The same, if ... else behind if only one statement to be executed, you can put them with conditional statements on the same line.
Examples
One line if else statements:
print("A") if a > b else print("B")
Else you can put multiple statements on the same line:
Examples
One line if else statements, there are three conditions:
print("A") if a > b else print("=") if a == b else print("B")
and
and/ With the keyword is a logical operator, for combining conditional statements:
Examples
Test a is greater than b, c is greater than a:
if a > b and c > a:
print("两个条件都成立")
or
or/ Or keyword is a logical operator, for combining conditional statements:
Examples
Whether a test than b, that is greater than a or c:
if a > b or a > c:
print("至少有一个条件成立")