Python循环语句中else的用法总结

x = True
if x:
 print 'x is true'
else:
 print 'x is not true'

mark = 40
is_pass = True if mark >= 50 else False
print "Pass? " + str(is_pass)

# 打印 `For loop completed the execution`
for i in range(10):
 print i
else:
 print 'For loop completed the execution'
# 不打印 `For loop completed the execution`
for i in range(10):
 print i
 if i == 5:
 break
else:
 print 'For loop completed the execution'

# 打印 `While loop execution completed`
a = 0
loop = 0
while a <= 10:
 print a
 loop += 1
 a += 1
else:
 print "While loop execution completed"
# 不打印 `While loop execution completed`
a = 50
loop = 0
while a > 10:
 print a
 if loop == 5:
 break
 a += 1
 loop += 1
else:
 print "While loop execution completed"

file_name = "result.txt"
try:
 f = open(file_name, 'r')
except IOError:
 print 'cannot open', file_name
else:
 # Executes only if file opened properly
 print file_name, 'has', len(f.readlines()), 'lines'
 f.close()