Pythonic way to print list items

问题:

I would like to know if there is a better way to print all objects in a Python list than this :

myList = [Person(\"Foo\"), Person(\"Bar\")]
print(\"\\n\".join(map(str, myList)))
Foo
Bar

I read this way is not really good :

myList = [Person(\"Foo\"), Person(\"Bar\")]
for p in myList:
    print(p)

Isn\'t there something like :

print(p) for p in myList

If not, my question is... why ? If we can do this kind of stuff with comprehensive lists, why not as a simple statement outside a list ?

回答1:

Assuming you are using Python 3.x:

print(*myList, sep=\'\\n\')

You can get the same behavior on Python 2.x using from __future__ import print_function, as noted by mgilson in comments.

With the print statement on Python 2.x you will need iteration of some kind, regarding your question about print(p) for p in myList not working, you can just use the following which does the same thing and is still one line:

for p in myList: print p

For a solution that uses \'\\n\'.join(), I prefer list comprehensions and generators over map() so I would probably use the following:

print \'\\n\'.join(str(p) for p in myList) 

回答2:

I use this all the time :

#!/usr/bin/python

l = [1,2,3,7] 
print \"\".join([str(x) for x in l])

回答3:

[print(a) for a in list] will give a bunch of None types at the end though it prints out all the items

回答4:

For Python 2.*:

If you overload the function __str__() for your Person class, you can omit the part with map(str, ...). Another way for this is creating a function, just like you wrote:

def write_list(lst):
    for item in lst:
        print str(item) 

...

write_list(MyList)

There is in Python 3.* the argument sep for the print() function. Take a look at documentation.

回答5:

Expanding @lucasg\'s answer (inspired by the comment it received):

To get a formatted list output, you can do something along these lines:

l = [1,2,5]
print \", \".join(\'%02d\'%x for x in l)

01, 02, 05

Now the \", \" provides the separator (only between items, not at the end) and the formatting string \'02d\'combined with %x gives a formatted string for each item x - in this case, formatted as an integer with two digits, left-filled with zeros.

回答6:

To display each content, I use:

mylist = [\'foo\', \'bar\']
indexval = 0
for i in range(len(mylist)):     
    print(mylist[indexval])
    indexval += 1

Example of using in a function:

def showAll(listname, startat):
   indexval = startat
   try:
      for i in range(len(mylist)):
         print(mylist[indexval])
         indexval = indexval + 1
   except IndexError:
      print(\'That index value you gave is out of range.\')

Hope I helped.

回答7:

I think this is the most convenient if you just want to see the content in the list:

myList = [\'foo\', \'bar\']
print(\'myList is %s\' % str(myList))

Simple, easy to read and can be used together with format string.

回答8:

OP\'s question is: does something like following exists, if not then why

print(p) for p in myList # doesn\'t work, OP\'s intuition

answer is, it does exist which is:

[p for p in myList] #works perfectly

Basically, use [] for list comprehension and get rid of print to avoiding printing None. To see why print prints None see this

回答9:

I recently made a password generator and although I\'m VERY NEW to python, I whipped this up as a way to display all items in a list (with small edits to fit your needs...

    x = 0
    up = 0
    passwordText = \"\"
    password = []
    userInput = int(input(\"Enter how many characters you want your password to be: \"))
    print(\"\\n\\n\\n\") # spacing

    while x <= (userInput - 1): #loops as many times as the user inputs above
            password.extend([choice(groups.characters)]) #adds random character from groups file that has all lower/uppercase letters and all numbers
            x = x+1 #adds 1 to x w/o using x ++1 as I get many errors w/ that
            passwordText = passwordText + password[up]
            up = up+1 # same as x increase


    print(passwordText)

Like I said, IM VERY NEW to Python and I\'m sure this is way to clunky for a expert, but I\'m just here for another example

回答10:

Assuming you are fine with your list being printed [1,2,3], then an easy way in Python3 is:

mylist=[1,2,3,\'lorem\',\'ipsum\',\'dolor\',\'sit\',\'amet\']

print(f\"There are {len(mylist):d} items in this lorem list: {str(mylist):s}\")

Running this produces the following output:

There are 8 items in this lorem list: [1, 2, 3, \'lorem\', \'ipsum\', \'dolor\', \'sit\', \'amet\']