擅长:python、mysql、java
<p>没有区别,因为len()是一个非常便宜的操作,您可以轻松地检查它:</p>
<pre><code>$ cat code1.py
#!/usr/bin/env python3
for x in range(10000):
list=[1,2,3,4,5]
for i in range(len(list)):
for j in range(len(list)):
print(i+j)
$ cat code2.py
#!/usr/bin/env python3
for x in range(10000):
list=[1,2,3,4,5]
l=len(list)
for i in range(l):
for j in range(l):
print(i)
$ time ./code1.py >> /dev/null
real 0m0.153s
user 0m0.152s
sys 0m0.000s
$ time ./code2.py >> /dev/null
real 0m0.156s
user 0m0.152s
sys 0m0.000s
</code></pre>