Python program structure
Python's program consists of packages, modules (that is, a Python file) and functions. A package is a collection of modules. A module is a collection of functions and classes that deal with a certain type of problem.
The package must contain at least one __init__.py file, and the content of this file can be empty. Used to identify the current folder as a package.
if statement
>;>;>; x = int(raw_input("Please enter an integer: "))
>;>;>; if x < 0:... x = 0... print 'Negative changed to zero'... elif x == 0:... print 'Zero'... elif x == 1:... print 'Single'... else:... print 'More'...##for statement>;>;>; # Measure some strings:
... a = ['cat', 'window', 'defenestrate']
>;>;>; for x in a:
... print x, len(x)
...
cat 3
window 6
defenestrate 12
Use The range function implements a counting loop>;>;>; for i in range(3): print i, 'Pythons'
...
0 Pythons
1 Pythons
2 Pythons
while statement>;>;>; x = 'spam'
>;>;>; while x:
... print x,
... x = x[1:]
...
spam pam am m
break continue pass else loop
- break jump out of the loop
continue jump to the top of the loop
pass does nothing, just a placeholder empty statement
else runs and only runs if the loop exits normally
while <条件测试>;： <语句>; if <条件测试>;: break #现在跳出循环，忽略else if <条件测试>;: continue #现在转到循环顶部 else: <语句>; #如果没有遇到break
