How to print the list in 'for' loop using .format() in Python?

Question

I'm a newbie to Python. I'm writing a very simple piece of code to print the contents of a list using 'for' loop with .format() and I want the output as below, but I'm getting this error:

names = ['David', 'Peter', 'Michael', 'John', 'Bob']
for i in names:
    print("{}.{}".format(i, names[i]))

print("{}.{}".format(i,breakfastMenu[i]))
TypeError: list indices must be integers or slices, not str

Expected output I want: 1. David 2. Peter 3. Michael 4. John 5. Bob

Can someone please help me to get that output?

Please format your code. Python is unreadable without proper indentation. Edit your comment and use the code formatting button. — gilch, Aug 11 '18 at 01:20
I'm still not certain about how you want the output formatted. Did you want them all on one line? — gilch, Aug 11 '18 at 01:24
hey @gilch ... Since this is my first post in Stack overflow ... I was not aware how to write the content properly :) ... I wrote the code properly with indent (taken care) in PyCharm IDE. And I wanted the output as below - 1. David \n2. Peter \n3. Michael \n4. John \n5. Bob — devPython, Aug 11 '18 at 01:35

score 5 · Accepted Answer · edited Aug 11 '18 at 01:28

5

names = ['David', 'Peter', 'Michael', 'John', 'Bob']
for i in range (len (names)):
    print("{}.{}".format(i + 1, names[i]))

Python list index references cannot be strings. Iterating through the list via a for loop using integers rather than the indexes themselves (which are strings) will solve this issue. This is an example where the error message is very useful in diagnosing the problem.

edited Aug 11 '18 at 01:28

Matias Cicero

25,439
13
82
154

answered Aug 11 '18 at 01:24

Reece

549
9
23

2

Thanks a lot @Matias Cicero .. This simple answer from your end helped me to understand the concept. – devPython Aug 11 '18 at 01:48

gilch · Answer 2 · 2018-08-11T01:28:39.897

2

Python's for...in statement is like like a foreach in other languages. You want enumerate to get the indexes.

for i, name in enumerate(names):
    print("{}. {}".format(i+1, name))

If you want to print them all on one line, use the end kwarg.

for i, name in enumerate(names):
    print("{}. {}".format(i+1, name), end=" ")
print()  # for the final newline

1. David 2. Peter 3. Michael 4. John 5. Bob

edited Aug 11 '18 at 01:28

answered Aug 11 '18 at 01:22

gilch

10,813
1
23
28

score 1 · Answer 3 · answered Aug 11 '18 at 01:24

names is a list of str, so, when you iterate over it, you'll get str values.

for i in names:
   print(i + 'other_str') # i is a str

In order to randomly access elements on a list, you need to specify their index, which needs to be an int.

If you want to get the correspondent indices of the elements, while you are iterating over them, you can use Python's enumerate:

for index, name, in enumerate(names):
    print('{}.{}'.format(index, names[index]))

Note that you don't really need to access the name by names[index] because you already get the element when iterating. So, the above is similar to the following:

for index, name in enumerate(names):
    print('{}.{}'.format(index, name))

Which outputs:

0.David
1.Peter
2.Michael
3.John
4.Bob

`index + 1` would output the names starting from 1 rather than 0. Small edit but makes for a better output. — Reece, Aug 11 '18 at 01:31

score 1 · Answer 4 · answered Aug 11 '18 at 02:01

Well, as per suggested answer from you guys I tried. I got the Expected output

>>> names = ['David', 'Peter', 'Michael', 'John', 'Bob']
>>> for i in range(len(names)):
    print('{}.{}'.format(i+1, names[i]))

Output I could see:

1.David
2.Peter
3.Michael
4.John
5.Bob

How to print the list in 'for' loop using .format() in Python?

4 Answers4

Linked