Python for loop examples

Frequently used python for loop examples.

python-for-loop-examples

For loop to iterate over a list

Iterate on each element of a list

a = ["v1", "v2", "v3"]
for val in a:
  print val
v1
v2
v3
Env: Python 2.7.6

Iterate on each index, element of a list

a = ["v1", "v2", "v3"]
for i,val in enumerate(a):
  print str(i) + " " + str(val)
0 v1
1 v2
2 v3
Env: Python 2.7.6

For loop to iterate over a string characters

s = "Hello"
for val in s:
  print val
H
e
l
l
o
Env: Python 2.7.6

For loop to iterate over a dictionary

Iterate over dictionary keys, values or both

d = {"k1":"v1", "k2":"v2", "k3":"v3"}
## or d.keys()
for key in d:
  print key

for val in d.values():
  print val

for key,val in d.items():
  print key, val
k3
k2
k1
v3
v2
v1
k3 v3
k2 v2
k1 v1
Env: Python 2.7.6

For loop to iterate over a dictionary using iterators

Iterate over dictionary keys, values or both using iterators. This does not create a new copy and may be little more memory efficient for large dictionaries.

d = {"k1":"v1", "k2":"v2", "k3":"v3"}
for key in d.iterkeys():
  print key

for val in d.itervalues():
  print val

for key,val in d.iteritems():
  print key, val
k3
k2
k1
v3
v2
v1
k3 v3
k2 v2
k1 v1
Env: Python 2.7.6

Share this article: share on Google+ share on facebook share on linkedin tweet this submit to reddit

Comments

Click here to write/view comments