diff --git a/src/calibre/gui2/store/stores/empik_plugin.py b/src/calibre/gui2/store/stores/empik_plugin.py
index 8a38ff8709..ae9c61344d 100644
--- a/src/calibre/gui2/store/stores/empik_plugin.py
+++ b/src/calibre/gui2/store/stores/empik_plugin.py
@@ -58,7 +58,7 @@ class EmpikStore(BasicStoreConfig, StorePlugin):
             d.exec_()
 
     def search(self, query, max_results=10, timeout=60):
-        url = 'http://www.empik.com/ebooki/ebooki,3501,s?resultsPP=' + str(max_results) + '&q=' + quote(query)
+        url = 'http://www.empik.com/ebooki/ebooki,3501,s?resultsPP={}&q={}'.format(max_results, quote(query))
 
         br = browser()
 
diff --git a/src/calibre/gui2/store/stores/nexto_plugin.py b/src/calibre/gui2/store/stores/nexto_plugin.py
index 74b45241c0..c05f2c2e3f 100644
--- a/src/calibre/gui2/store/stores/nexto_plugin.py
+++ b/src/calibre/gui2/store/stores/nexto_plugin.py
@@ -57,7 +57,7 @@ class NextoStore(BasicStoreConfig, StorePlugin):
         counter = max_results
 
         while counter:
-            with closing(br.open(url + '&_offset=' + str(offset), timeout=timeout)) as f:
+            with closing(br.open(url + '&_offset={}'.format(offset), timeout=timeout)) as f:
                 doc = html.fromstring(f.read())
                 for data in doc.xpath('//ul[@class="productslist"]/li'):
                     if counter <= 0:
@@ -76,7 +76,7 @@ class NextoStore(BasicStoreConfig, StorePlugin):
                     title = re.sub(r' – ebook', '', title)
                     author = ', '.join(data.xpath('.//div[@class="col-7"]//h4//a/text()'))
                     formats = ', '.join(data.xpath('.//ul[@class="formats"]/li//b/text()'))
-                    DrmFree = re.search(r'znak', str(data.xpath('.//ul[@class="formats"]/li//b/@title')))
+                    DrmFree = re.search(r'znak', type('')(data.xpath('.//ul[@class="formats"]/li//b/@title')))
 
                     counter -= 1
 
diff --git a/src/calibre/gui2/store/stores/publio_plugin.py b/src/calibre/gui2/store/stores/publio_plugin.py
index c5fc9b8bf7..da5fdee3bf 100644
--- a/src/calibre/gui2/store/stores/publio_plugin.py
+++ b/src/calibre/gui2/store/stores/publio_plugin.py
@@ -62,7 +62,7 @@ class PublioStore(BasicStoreConfig, StorePlugin):
         counter = max_results
         page = 1
         while counter:
-            with closing(br.open('http://www.publio.pl/e-booki,strona' + str(page) + '.html?q=' + quote(query), timeout=timeout)) as f:  # noqa
+            with closing(br.open('http://www.publio.pl/e-booki,strona{}.html?q={}'.format(page, quote(query)), timeout=timeout)) as f:  # noqa
                 doc = html.fromstring(f.read())
                 for data in doc.xpath('//div[@class="products-list"]//div[@class="product-tile"]'):
                     if counter <= 0:
diff --git a/src/calibre/gui2/store/stores/swiatebookow_plugin.py b/src/calibre/gui2/store/stores/swiatebookow_plugin.py
index 373dc07a72..ec884e3f09 100644
--- a/src/calibre/gui2/store/stores/swiatebookow_plugin.py
+++ b/src/calibre/gui2/store/stores/swiatebookow_plugin.py
@@ -63,7 +63,7 @@ class SwiatEbookowStore(BasicStoreConfig, StorePlugin):
 
         counter = max_results
         while counter:
-            with closing(br.open('https://www.swiatebookow.pl/ebooki/?q=' + quote(query) + '&page=' + str(page), timeout=timeout)) as f:
+            with closing(br.open('https://www.swiatebookow.pl/ebooki/?q=' + quote(query) + '&page={}'.format(page), timeout=timeout)) as f:
                 doc = html.fromstring(f.read().decode('utf-8'))
                 for data in doc.xpath('//div[@class="category-item-container"]//div[@class="book-large"]'):
                     if counter <= 0: